build(project): install vips-tools for image thumbnailing

Add vips-tools (vipsthumbnail) to the runtime image alongside ffmpeg and
exiftool, and document THUMB_MAX_PIXELS as the pure-Go fallback guard.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

.dockerignore

@@ -0,0 +1,33 @@
+# Keep the build context small and reproducible: never ship local state,
+# dependencies, or build outputs — they are rebuilt inside the image.
+
+# VCS / tooling
+.git
+.gitignore
+**/.DS_Store
+
+# Compose file — used to build/run, not needed inside the image context
+docker-compose.yml
+docker-compose.*.yml
+
+# Secrets and local env
+.env
+.env.*
+!.env.example
+
+# Node
+frontend/node_modules
+frontend/.svelte-kit
+frontend/build
+frontend/.vite
+
+# Go
+backend/server
+backend/**/*.test
+
+# Docs / reference (not needed to build the image)
+docs/reference
+
+# Editor / OS
+.vscode
+.idea

.env.example

@@ -0,0 +1,118 @@
+# =============================================================================
+# Tanabata File Manager — environment variables
+#
+# Copy to .env and fill in the secrets:
+#   cp .env.example .env
+#   docker compose up -d --build
+# =============================================================================
+
+# ---------------------------------------------------------------------------
+# Docker Compose  (read by the compose CLI, ignored by the app)
+# ---------------------------------------------------------------------------
+# Profiles to enable. "with-db" runs the bundled Postgres container. Leave
+# EMPTY to skip it and use a Postgres running on the host instead — then point
+# DATABASE_URL at host.docker.internal (see the Database section below).
+COMPOSE_PROFILES=with-db
+
+# Host port the app is published on. The container always listens on 42776.
+APP_PORT=42776
+
+# ---------------------------------------------------------------------------
+# Volume mounts  (Docker Compose; ignored by the app)
+# ---------------------------------------------------------------------------
+# By default the app's data and the database live in named Docker volumes
+# (app_files, app_thumbs, app_import, db_data). To keep them in specific folders
+# on the host instead, point any of these at a host path — absolute, or relative
+# to this file (e.g. ./data/files). Unset = named volume.
+# FILES_DIR=/var/lib/tanabata/files
+# THUMBS_DIR=/var/lib/tanabata/thumbs
+# IMPORT_DIR=/var/lib/tanabata/import
+# DB_DIR=/var/lib/tanabata/db
+
+# When bind-mounting the app folders above, the container must be able to write
+# to them. Set PUID/PGID to the owner of those folders and create them with
+# matching ownership first, e.g.:
+#   sudo mkdir -p /var/lib/tanabata/{files,thumbs,import}
+#   sudo chown -R 1000:1000 /var/lib/tanabata
+#   PUID=1000
+#   PGID=1000
+# Defaults match the image's tanabata user (42776), which owns the named volumes. The
+# DB folder is handled by Postgres itself and needs no PUID/PGID.
+# PUID=42776
+# PGID=42776
+
+# ---------------------------------------------------------------------------
+# Server
+# ---------------------------------------------------------------------------
+# 42776 is the project's default port: the sum of the Unicode code points of
+# 七夕 (七 U+4E03 = 19971, 夕 U+5915 = 22805).
+LISTEN_ADDR=:42776
+JWT_SECRET=change-me-to-a-random-32-byte-secret
+JWT_ACCESS_TTL=15m
+JWT_REFRESH_TTL=720h
+
+# Initial administrator, created on first startup if it does not yet exist.
+# Changing the password later (via the API) is preserved across restarts.
+ADMIN_USERNAME=admin
+ADMIN_PASSWORD=change-me-before-first-run
+
+# ---------------------------------------------------------------------------
+# Database
+# ---------------------------------------------------------------------------
+# Credentials for the bundled Postgres container (the "with-db" profile).
+# Keep these in sync with DATABASE_URL below.
+POSTGRES_DB=tanabata
+POSTGRES_USER=tanabata
+POSTGRES_PASSWORD=password
+
+# Connection string the app uses. Pick ONE to match your database mode:
+#
+#   • Bundled container DB (COMPOSE_PROFILES=with-db) — host is the "db" service:
+DATABASE_URL=postgres://tanabata:password@db:5432/tanabata?sslmode=disable
+#
+#   • Postgres on the host (COMPOSE_PROFILES empty):
+# DATABASE_URL=postgres://tanabata:password@host.docker.internal:5432/tanabata?sslmode=disable
+#
+#   • Bare-metal `go run` (no Docker):
+# DATABASE_URL=postgres://tanabata:password@localhost:5432/tanabata?sslmode=disable
+
+# ---------------------------------------------------------------------------
+# Storage  (paths inside the container; backed by named volumes in compose)
+# ---------------------------------------------------------------------------
+FILES_PATH=/data/files
+THUMBS_CACHE_PATH=/data/thumbs
+
+# Maximum accepted upload size in bytes (default 500 MiB).
+MAX_UPLOAD_BYTES=524288000
+
+# ---------------------------------------------------------------------------
+# Thumbnails
+# ---------------------------------------------------------------------------
+THUMB_WIDTH=160
+THUMB_HEIGHT=160
+PREVIEW_WIDTH=1920
+PREVIEW_HEIGHT=1080
+# Pixel cap (width×height) for the pure-Go fallback decoder, used only when
+# vipsthumbnail is NOT installed; larger images then get a placeholder. With vips
+# present (the default image) thumbnails shrink on load, so this limit — and its
+# RAM cost — don't apply. Also bounds a decompression bomb. Default ~300 Mpx.
+THUMB_MAX_PIXELS=300000000
+# How many thumbnails/previews may be generated at once. Each resize already uses
+# every core, so a burst of large images otherwise pegs the CPU and RAM. 0 = auto
+# (half the available CPUs).
+THUMB_CONCURRENCY=0
+
+# ---------------------------------------------------------------------------
+# Import
+# ---------------------------------------------------------------------------
+IMPORT_PATH=/data/import
+
+# ---------------------------------------------------------------------------
+# Static SPA
+# ---------------------------------------------------------------------------
+# Leave UNSET here. The Docker image already serves the built SPA from
+# /app/static and compose pins STATIC_DIR for the container — an empty value in
+# .env would be injected into the container and disable SPA serving. Set this
+# only for a bare-metal deploy where the Go server serves a built SPA; leave it
+# unset in local dev, where the Vite dev server serves the UI.
+# STATIC_DIR=/path/to/frontend/build

.gitattributes

@@ -0,0 +1,67 @@
+# =============================================================================
+# Tanabata File Manager — .gitattributes
+# =============================================================================
+
+# ---------------------------------------------------------------------------
+# Line endings: normalize to LF in repo, native on checkout
+# ---------------------------------------------------------------------------
+* text=auto eol=lf
+
+# ---------------------------------------------------------------------------
+# Explicitly text
+# ---------------------------------------------------------------------------
+*.go        text eol=lf
+*.mod       text eol=lf
+*.sum       text eol=lf
+*.sql       text eol=lf
+*.ts        text eol=lf
+*.js        text eol=lf
+*.svelte    text eol=lf
+*.html      text eol=lf
+*.css       text eol=lf
+*.json      text eol=lf
+*.yaml      text eol=lf
+*.yml       text eol=lf
+*.md        text eol=lf
+*.txt       text eol=lf
+*.env*      text eol=lf
+*.sh        text eol=lf
+*.toml      text eol=lf
+*.xml       text eol=lf
+*.svg       text eol=lf
+Dockerfile  text eol=lf
+Makefile    text eol=lf
+
+# ---------------------------------------------------------------------------
+# Explicitly binary
+# ---------------------------------------------------------------------------
+*.png       binary
+*.jpg       binary
+*.jpeg      binary
+*.gif       binary
+*.webp      binary
+*.ico       binary
+*.ttf       binary
+*.woff      binary
+*.woff2     binary
+*.eot       binary
+*.otf       binary
+*.zip       binary
+*.gz        binary
+*.tar       binary
+
+# ---------------------------------------------------------------------------
+# Diff behavior
+# ---------------------------------------------------------------------------
+*.sql       diff=sql
+*.go        diff=golang
+*.css       diff=css
+*.html      diff=html
+
+# ---------------------------------------------------------------------------
+# Linguist: set repo language stats correctly
+# ---------------------------------------------------------------------------
+docs/reference/** linguist-documentation
+frontend/static/** linguist-vendored
+*.min.js linguist-vendored
+*.min.css linguist-vendored

.gitea/workflows/deploy.yml

@@ -0,0 +1,44 @@
+name: deploy
+
+# Build the image and (re)start the compose stack on the production host
+# whenever master moves. Also runnable manually from the Gitea Actions tab.
+on:
+  push:
+    branches: [master]
+  workflow_dispatch: {}
+
+# One deploy at a time; queue rather than cancel an in-flight run.
+concurrency:
+  group: deploy-prod
+  cancel-in-progress: false
+
+jobs:
+  deploy:
+    # Self-hosted act_runner registered on the prod host with the "host" label
+    # (shell executor), so the job uses the host's git + Docker daemon and the
+    # existing clone in /opt/tanabata. See docs/DEPLOY.md for runner setup.
+    #
+    # Only shell steps here (no `uses:` actions), so the host needs git + docker
+    # and nothing else — no node, no rsync.
+    runs-on: host
+
+    env:
+      DEPLOY_DIR: /opt/tanabata
+
+    steps:
+      - name: Pull latest master
+        # DEPLOY_DIR is a git clone set up once at deploy time. reset --hard
+        # makes it match origin exactly; .env is untracked (.gitignore) so it
+        # is never touched.
+        run: |
+          cd "$DEPLOY_DIR"
+          git fetch --prune origin
+          git reset --hard origin/master
+
+      - name: Build image and start the stack
+        working-directory: /opt/tanabata
+        # .env must already exist in DEPLOY_DIR on the host (secrets + DB mode).
+        run: docker compose up -d --build --remove-orphans
+
+      - name: Prune dangling build layers
+        run: docker image prune -f

.gitignore

@@ -1,3 +1,86 @@
-venv/
-*__pycache__/
-.st*
+# =============================================================================
+# Tanabata File Manager — .gitignore
+# =============================================================================
+
+# ---------------------------------------------------------------------------
+# Environment & secrets
+# ---------------------------------------------------------------------------
+.env
+.env.local
+.env.*.local
+*.pem
+*.key
+
+# ---------------------------------------------------------------------------
+# OS
+# ---------------------------------------------------------------------------
+.DS_Store
+Thumbs.db
+Desktop.ini
+*.swp
+*.swo
+*~
+
+# ---------------------------------------------------------------------------
+# IDE
+# ---------------------------------------------------------------------------
+.vscode/*
+!.vscode/extensions.json
+!.vscode/settings.json
+.idea/
+*.iml
+*.sublime-project
+*.sublime-workspace
+
+# ---------------------------------------------------------------------------
+# Backend (Go)
+# ---------------------------------------------------------------------------
+backend/tmp/
+backend/cmd/server/server
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+*.test
+*.out
+*.prof
+coverage.out
+coverage.html
+
+# ---------------------------------------------------------------------------
+# Frontend (SvelteKit / Node)
+# ---------------------------------------------------------------------------
+frontend/node_modules/
+frontend/.svelte-kit/
+frontend/build/
+frontend/dist/
+frontend/src/lib/api/schema.ts
+
+# ---------------------------------------------------------------------------
+# Docker
+# ---------------------------------------------------------------------------
+docker-compose.override.yml
+
+# ---------------------------------------------------------------------------
+# Data directories (runtime, not in repo)
+# ---------------------------------------------------------------------------
+data/
+*.sqlite
+*.sqlite3
+
+# ---------------------------------------------------------------------------
+# Misc
+# ---------------------------------------------------------------------------
+*.log
+*.pid
+*.seed
+
+# ---------------------------------------------------------------------------
+# Reference: exclude vendored libs, keep design sources
+# ---------------------------------------------------------------------------
+docs/reference/**/bootstrap.min.css
+docs/reference/**/bootstrap.min.css.map
+docs/reference/**/jquery-*.min.js
+docs/reference/**/__pycache__/
+docs/reference/**/*.pyc

CLAUDE.md

@@ -0,0 +1,58 @@
+# Tanabata File Manager
+
+Multi-user, tag-based web file manager for images and video.
+
+## Architecture
+
+Monorepo: `backend/` (Go) + `frontend/` (SvelteKit).
+
+- Backend: Go + Gin + pgx v5 + goose migrations. Clean Architecture.
+- Frontend: SvelteKit SPA + Tailwind CSS + CSS custom properties.
+- DB: PostgreSQL 14+.
+- Auth: JWT Bearer tokens.
+
+## Key documents (read before coding)
+
+- `openapi.yaml` — full REST API specification (36 paths, 58 operations)
+- `docs/GO_PROJECT_STRUCTURE.md` — backend architecture, layer rules, DI pattern
+- `docs/FRONTEND_STRUCTURE.md` — frontend architecture, CSS approach, API client
+- `docs/Описание.md` — product requirements in Russian
+- `backend/migrations/001_init.sql` — database schema (4 schemas, 16 tables)
+
+## Design reference
+
+The `docs/reference/` directory contains the previous Python/Flask version.
+Use its visual design as the basis for the new frontend:
+- Color palette: #312F45 (bg), #9592B5 (accent), #444455 (tag default), #111118 (elevated)
+- Font: Epilogue (variable weight)
+- Dark theme is primary
+- Mobile-first layout with bottom navbar
+- 160×160 thumbnail grid for files
+- Colored tag pills
+- Floating selection bar for multi-select
+
+## Backend commands
+```bash
+cd backend
+go run ./cmd/server          # run dev server
+go test ./...                # run all tests
+```
+
+## Frontend commands
+```bash
+cd frontend
+npm run dev                  # vite dev server
+npm run build                # production build
+npm run generate:types       # regenerate API types from openapi.yaml
+```
+
+## Conventions
+
+- Go: gofmt, no global state, context.Context as first param in all service methods
+- TypeScript: strict mode, named exports
+- SQL: snake_case, all migrations via goose
+- API errors: { code, message, details? }
+- Git: conventional commits with scope — `type(scope): message`
+  - `(backend)` for Go backend code
+  - `(frontend)` for SvelteKit/TypeScript code
+  - `(project)` for root-level files (.gitignore, docs/reference, structure)

Dockerfile

@@ -0,0 +1,93 @@
+# syntax=docker/dockerfile:1
+
+# =============================================================================
+# Tanabata File Manager — single-image build
+#
+# Produces one container that serves the SvelteKit SPA (built to static files)
+# and the Go API on the same port. There is no Node runtime in the final image:
+# the frontend uses adapter-static, so stage 1 emits plain HTML/CSS/JS that the
+# Go binary serves directly (see STATIC_DIR).
+# =============================================================================
+
+# -----------------------------------------------------------------------------
+# Stage 1 — build the frontend (static SPA)
+# -----------------------------------------------------------------------------
+FROM node:22-alpine AS frontend
+
+WORKDIR /src/frontend
+
+# Install dependencies first so this layer is cached unless the lockfile changes.
+COPY frontend/package.json frontend/package-lock.json ./
+RUN npm ci
+
+# `npm run build` runs `generate:types`, which reads ../openapi.yaml relative to
+# the frontend directory — place the spec one level up to match the repo layout.
+COPY openapi.yaml /src/openapi.yaml
+COPY frontend/ ./
+
+RUN npm run build
+# Output: /src/frontend/build (index.html, _app/, fonts, service-worker.js, …)
+
+# -----------------------------------------------------------------------------
+# Stage 2 — build the Go server (static binary)
+# -----------------------------------------------------------------------------
+FROM golang:1.26-alpine AS backend
+
+WORKDIR /src/backend
+
+# Download modules first so this layer is cached unless go.mod/go.sum changes.
+COPY backend/go.mod backend/go.sum ./
+RUN go mod download
+
+COPY backend/ ./
+
+# CGO is disabled: the binary shells out to external tools at runtime
+# (vipsthumbnail for image thumbnails, ffmpeg for video frames, exiftool for
+# metadata) and falls back to pure-Go image processing (disintegration/imaging)
+# when vips is absent, so it stays fully static and portable across base images.
+RUN CGO_ENABLED=0 GOOS=linux go build -trimpath -ldflags="-s -w" -o /out/server ./cmd/server
+
+# -----------------------------------------------------------------------------
+# Stage 3 — minimal runtime
+#
+# Alpine (not distroless/scratch) because thumbnailing and metadata extraction
+# invoke external processes (vipsthumbnail, ffmpeg, exiftool) that must be present
+# on the runtime image.
+# -----------------------------------------------------------------------------
+FROM alpine:3.21 AS runtime
+
+# vips-tools: fast, low-memory image thumbnails (shrink-on-load, so multi-hundred-
+# Mpx photos cost little). ffmpeg: video frame extraction. exiftool: rich metadata.
+# ca-certificates/tzdata: TLS + time zones.
+RUN apk add --no-cache vips-tools ffmpeg exiftool ca-certificates tzdata
+
+# Run as an unprivileged user.
+RUN addgroup -S -g 42776 tanabata && adduser -S -G tanabata -u 42776 tanabata
+
+WORKDIR /app
+
+# The built SPA, served by the Go binary (matches STATIC_DIR below).
+COPY --from=frontend --chown=tanabata:tanabata /src/frontend/build /app/static
+# The server binary.
+COPY --from=backend --chown=tanabata:tanabata /out/server /app/server
+
+# Data directories (overridable via FILES_PATH/THUMBS_CACHE_PATH/IMPORT_PATH).
+# Created and owned by the tanabata user so a fresh named volume inherits write access.
+RUN mkdir -p /data/files /data/thumbs /data/import && chown -R tanabata:tanabata /data
+
+# Non-secret defaults mirroring .env.example. Secrets (JWT_SECRET, ADMIN_PASSWORD,
+# DATABASE_URL) are intentionally NOT baked in — pass them at `docker run`.
+ENV LISTEN_ADDR=:42776 \
+    STATIC_DIR=/app/static \
+    FILES_PATH=/data/files \
+    THUMBS_CACHE_PATH=/data/thumbs \
+    IMPORT_PATH=/data/import
+
+EXPOSE 42776
+VOLUME ["/data"]
+USER tanabata
+
+HEALTHCHECK --interval=30s --timeout=3s --start-period=10s --retries=3 \
+    CMD wget -qO- http://127.0.0.1:42776/health >/dev/null 2>&1 || exit 1
+
+ENTRYPOINT ["/app/server"]

README.md

@@ -1,22 +0,0 @@
-<h1 align="center">🎋 Tanabata File Manager 🎋</h1>
-
----
-
-<!-- [![Release version][release-shield]][release-link] -->
-
-## Contents
-
-- [About](#about)
-
-## About
-
-Tanabata (_jp._ 七夕) is Japanese festival. People generally celebrate this day (July 7th) by writing wishes, sometimes in the form of poetry, on _tanzaku_ (_jp._ 短冊), small pieces of paper, and hanging them on _sasa_ (_jp._ 笹), bamboo. See [this Wikipedia page](https://en.wikipedia.org/wiki/Tanabata) for more information.
-
-Tanabata File Manager is a software project that will let you enjoy the Tanabata festival. It allows you to store and organize your files as _sasa_ bamboos, on which you can hang almost any number of _tanzaku_, just like adding tags on it.
-
----
-
-<h6 align="center"><i>&copy; Masahiko AMANO aka H1K0, 2022—present</i></h6>
-
-<!-- [release-shield]: https://img.shields.io/github/release/H1K0/tanabata/all.svg?style=for-the-badge
-[release-link]: https://github.com/H1K0/tanabata/releases -->

_config.yml

@@ -1,5 +0,0 @@
-title: Tanabata FM
-description: Web file manager with tags!
-remote_theme: pages-themes/merlot@v0.2.0
-plugins:
-  - jekyll-remote-theme

backend/cmd/server/main.go

@@ -0,0 +1,138 @@
+package main
+
+import (
+	"context"
+	"log/slog"
+	"net/http"
+	"os"
+	"time"
+
+	"github.com/jackc/pgx/v5/stdlib"
+	"github.com/pressly/goose/v3"
+
+	"tanabata/backend/internal/config"
+	"tanabata/backend/internal/db/postgres"
+	"tanabata/backend/internal/handler"
+	"tanabata/backend/internal/service"
+	"tanabata/backend/internal/storage"
+	"tanabata/backend/migrations"
+)
+
+func main() {
+	cfg, err := config.Load()
+	if err != nil {
+		slog.Error("failed to load config", "err", err)
+		os.Exit(1)
+	}
+
+	pool, err := postgres.NewPool(context.Background(), cfg.DatabaseURL)
+	if err != nil {
+		slog.Error("failed to connect to database", "err", err)
+		os.Exit(1)
+	}
+	defer pool.Close()
+	slog.Info("database connected")
+
+	migDB := stdlib.OpenDBFromPool(pool)
+	goose.SetBaseFS(migrations.FS)
+	if err := goose.SetDialect("postgres"); err != nil {
+		slog.Error("goose dialect error", "err", err)
+		os.Exit(1)
+	}
+	if err := goose.Up(migDB, "."); err != nil {
+		slog.Error("migrations failed", "err", err)
+		os.Exit(1)
+	}
+	migDB.Close()
+	slog.Info("migrations applied")
+
+	// Storage
+	diskStorage, err := storage.NewDiskStorage(
+		cfg.FilesPath,
+		cfg.ThumbsCachePath,
+		cfg.ThumbWidth, cfg.ThumbHeight,
+		cfg.PreviewWidth, cfg.PreviewHeight,
+		cfg.ThumbMaxPixels, cfg.ThumbConcurrency,
+	)
+	if err != nil {
+		slog.Error("failed to initialise storage", "err", err)
+		os.Exit(1)
+	}
+
+	// Repositories
+	userRepo := postgres.NewUserRepo(pool)
+	sessionRepo := postgres.NewSessionRepo(pool)
+	fileRepo := postgres.NewFileRepo(pool)
+	mimeRepo := postgres.NewMimeRepo(pool)
+	aclRepo := postgres.NewACLRepo(pool)
+	auditRepo := postgres.NewAuditRepo(pool)
+	tagRepo := postgres.NewTagRepo(pool)
+	tagRuleRepo := postgres.NewTagRuleRepo(pool)
+	categoryRepo := postgres.NewCategoryRepo(pool)
+	poolRepo := postgres.NewPoolRepo(pool)
+	transactor := postgres.NewTransactor(pool)
+
+	// Services
+	authSvc := service.NewAuthService(
+		userRepo,
+		sessionRepo,
+		cfg.JWTSecret,
+		cfg.JWTAccessTTL,
+		cfg.JWTRefreshTTL,
+	)
+	aclSvc := service.NewACLService(aclRepo, fileRepo, tagRepo, categoryRepo, poolRepo, transactor)
+	auditSvc := service.NewAuditService(auditRepo)
+	tagSvc := service.NewTagService(tagRepo, tagRuleRepo, aclSvc, auditSvc, transactor)
+	categorySvc := service.NewCategoryService(categoryRepo, tagRepo, aclSvc, auditSvc)
+	poolSvc := service.NewPoolService(poolRepo, aclSvc, auditSvc)
+	fileSvc := service.NewFileService(
+		fileRepo,
+		mimeRepo,
+		diskStorage,
+		aclSvc,
+		auditSvc,
+		tagSvc,
+		transactor,
+		cfg.ImportPath,
+	)
+	userSvc := service.NewUserService(userRepo, sessionRepo, auditSvc)
+
+	// Bootstrap the initial administrator (idempotent).
+	if err := userSvc.EnsureAdmin(context.Background(), cfg.AdminUsername, cfg.AdminPassword); err != nil {
+		slog.Error("failed to bootstrap admin user", "err", err)
+		os.Exit(1)
+	}
+
+	// Handlers
+	authMiddleware := handler.NewAuthMiddleware(authSvc)
+	authHandler := handler.NewAuthHandler(authSvc)
+	fileHandler := handler.NewFileHandler(fileSvc, tagSvc, cfg.MaxUploadBytes)
+	tagHandler := handler.NewTagHandler(tagSvc, fileSvc)
+	categoryHandler := handler.NewCategoryHandler(categorySvc)
+	poolHandler := handler.NewPoolHandler(poolSvc)
+	userHandler := handler.NewUserHandler(userSvc)
+	aclHandler := handler.NewACLHandler(aclSvc)
+	auditHandler := handler.NewAuditHandler(auditSvc)
+
+	r := handler.NewRouter(
+		authMiddleware, authHandler,
+		fileHandler, tagHandler, categoryHandler, poolHandler,
+		userHandler, aclHandler, auditHandler,
+		cfg.StaticDir,
+	)
+
+	// ReadHeaderTimeout bounds slow-header (Slowloris) attacks; body read/write
+	// are left unbounded so large file uploads and downloads can stream.
+	srv := &http.Server{
+		Addr:              cfg.ListenAddr,
+		Handler:           r,
+		ReadHeaderTimeout: 10 * time.Second,
+		IdleTimeout:       120 * time.Second,
+	}
+
+	slog.Info("starting server", "addr", cfg.ListenAddr)
+	if err := srv.ListenAndServe(); err != nil {
+		slog.Error("server error", "err", err)
+		os.Exit(1)
+	}
+}

backend/go.mod

@@ -0,0 +1,104 @@
+module tanabata/backend
+
+go 1.26
+
+toolchain go1.26.1
+
+require (
+	github.com/disintegration/imaging v1.6.2
+	github.com/gabriel-vasile/mimetype v1.4.12
+	github.com/gin-gonic/gin v1.9.1
+	github.com/golang-jwt/jwt/v5 v5.3.1
+	github.com/google/uuid v1.6.0
+	github.com/jackc/pgx/v5 v5.5.5
+	github.com/joho/godotenv v1.5.1
+	github.com/pressly/goose/v3 v3.21.1
+	github.com/rwcarlsen/goexif v0.0.0-20190401172101-9e8deecbddbd
+	github.com/stretchr/testify v1.11.1
+	github.com/testcontainers/testcontainers-go v0.41.0
+	github.com/testcontainers/testcontainers-go/modules/postgres v0.41.0
+	golang.org/x/crypto v0.48.0
+	golang.org/x/image v0.0.0-20191009234506-e7c1f5e7dbb8
+)
+
+require (
+	dario.cat/mergo v1.0.2 // indirect
+	github.com/Azure/go-ansiterm v0.0.0-20250102033503-faa5f7b0171c // indirect
+	github.com/Microsoft/go-winio v0.6.2 // indirect
+	github.com/bytedance/gopkg v0.1.3 // indirect
+	github.com/bytedance/sonic v1.15.0 // indirect
+	github.com/bytedance/sonic/loader v0.5.0 // indirect
+	github.com/cenkalti/backoff/v4 v4.3.0 // indirect
+	github.com/cespare/xxhash/v2 v2.3.0 // indirect
+	github.com/cloudwego/base64x v0.1.6 // indirect
+	github.com/containerd/errdefs v1.0.0 // indirect
+	github.com/containerd/errdefs/pkg v0.3.0 // indirect
+	github.com/containerd/log v0.1.0 // indirect
+	github.com/containerd/platforms v0.2.1 // indirect
+	github.com/cpuguy83/dockercfg v0.3.2 // indirect
+	github.com/davecgh/go-spew v1.1.1 // indirect
+	github.com/distribution/reference v0.6.0 // indirect
+	github.com/docker/docker v28.5.2+incompatible // indirect
+	github.com/docker/go-connections v0.6.0 // indirect
+	github.com/docker/go-units v0.5.0 // indirect
+	github.com/ebitengine/purego v0.10.0 // indirect
+	github.com/felixge/httpsnoop v1.0.4 // indirect
+	github.com/gin-contrib/sse v0.1.0 // indirect
+	github.com/go-logr/logr v1.4.3 // indirect
+	github.com/go-logr/stdr v1.2.2 // indirect
+	github.com/go-ole/go-ole v1.2.6 // indirect
+	github.com/go-playground/locales v0.14.1 // indirect
+	github.com/go-playground/universal-translator v0.18.1 // indirect
+	github.com/go-playground/validator/v10 v10.22.0 // indirect
+	github.com/goccy/go-json v0.10.5 // indirect
+	github.com/grpc-ecosystem/grpc-gateway/v2 v2.28.0 // indirect
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
+	github.com/jackc/puddle/v2 v2.2.1 // indirect
+	github.com/json-iterator/go v1.1.12 // indirect
+	github.com/klauspost/compress v1.18.2 // indirect
+	github.com/klauspost/cpuid/v2 v2.2.9 // indirect
+	github.com/leodido/go-urn v1.4.0 // indirect
+	github.com/lufia/plan9stats v0.0.0-20211012122336-39d0f177ccd0 // indirect
+	github.com/magiconair/properties v1.8.10 // indirect
+	github.com/mattn/go-isatty v0.0.20 // indirect
+	github.com/mfridman/interpolate v0.0.2 // indirect
+	github.com/moby/docker-image-spec v1.3.1 // indirect
+	github.com/moby/go-archive v0.2.0 // indirect
+	github.com/moby/patternmatcher v0.6.0 // indirect
+	github.com/moby/sys/sequential v0.6.0 // indirect
+	github.com/moby/sys/user v0.4.0 // indirect
+	github.com/moby/sys/userns v0.1.0 // indirect
+	github.com/moby/term v0.5.2 // indirect
+	github.com/modern-go/concurrent v0.0.0-20180306012644-bacd9c7ef1dd // indirect
+	github.com/modern-go/reflect2 v1.0.2 // indirect
+	github.com/morikuni/aec v1.0.0 // indirect
+	github.com/opencontainers/go-digest v1.0.0 // indirect
+	github.com/opencontainers/image-spec v1.1.1 // indirect
+	github.com/pelletier/go-toml/v2 v2.2.4 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	github.com/pmezard/go-difflib v1.0.0 // indirect
+	github.com/power-devops/perfstat v0.0.0-20240221224432-82ca36839d55 // indirect
+	github.com/sethvargo/go-retry v0.3.0 // indirect
+	github.com/shirou/gopsutil/v4 v4.26.2 // indirect
+	github.com/sirupsen/logrus v1.9.3 // indirect
+	github.com/tklauser/go-sysconf v0.3.16 // indirect
+	github.com/tklauser/numcpus v0.11.0 // indirect
+	github.com/twitchyliquid64/golang-asm v0.15.1 // indirect
+	github.com/ugorji/go/codec v1.3.1 // indirect
+	github.com/yusufpapurcu/wmi v1.2.4 // indirect
+	go.opentelemetry.io/auto/sdk v1.2.1 // indirect
+	go.opentelemetry.io/contrib/instrumentation/net/http/otelhttp v0.49.0 // indirect
+	go.opentelemetry.io/otel v1.41.0 // indirect
+	go.opentelemetry.io/otel/metric v1.41.0 // indirect
+	go.opentelemetry.io/otel/trace v1.41.0 // indirect
+	go.uber.org/multierr v1.11.0 // indirect
+	golang.org/x/arch v0.22.0 // indirect
+	golang.org/x/net v0.49.0 // indirect
+	golang.org/x/sync v0.19.0 // indirect
+	golang.org/x/sys v0.41.0 // indirect
+	golang.org/x/text v0.34.0 // indirect
+	google.golang.org/grpc v1.79.1 // indirect
+	google.golang.org/protobuf v1.36.11 // indirect
+	gopkg.in/yaml.v3 v3.0.1 // indirect
+)

backend/go.sum

@@ -0,0 +1,275 @@
+dario.cat/mergo v1.0.2 h1:85+piFYR1tMbRrLcDwR18y4UKJ3aH1Tbzi24VRW1TK8=
+dario.cat/mergo v1.0.2/go.mod h1:E/hbnu0NxMFBjpMIE34DRGLWqDy0g5FuKDhCb31ngxA=
+github.com/AdaLogics/go-fuzz-headers v0.0.0-20240806141605-e8a1dd7889d6 h1:He8afgbRMd7mFxO99hRNu+6tazq8nFF9lIwo9JFroBk=
+github.com/AdaLogics/go-fuzz-headers v0.0.0-20240806141605-e8a1dd7889d6/go.mod h1:8o94RPi1/7XTJvwPpRSzSUedZrtlirdB3r9Z20bi2f8=
+github.com/Azure/go-ansiterm v0.0.0-20250102033503-faa5f7b0171c h1:udKWzYgxTojEKWjV8V+WSxDXJ4NFATAsZjh8iIbsQIg=
+github.com/Azure/go-ansiterm v0.0.0-20250102033503-faa5f7b0171c/go.mod h1:xomTg63KZ2rFqZQzSB4Vz2SUXa1BpHTVz9L5PTmPC4E=
+github.com/Microsoft/go-winio v0.6.2 h1:F2VQgta7ecxGYO8k3ZZz3RS8fVIXVxONVUPlNERoyfY=
+github.com/Microsoft/go-winio v0.6.2/go.mod h1:yd8OoFMLzJbo9gZq8j5qaps8bJ9aShtEA8Ipt1oGCvU=
+github.com/bytedance/gopkg v0.1.3 h1:TPBSwH8RsouGCBcMBktLt1AymVo2TVsBVCY4b6TnZ/M=
+github.com/bytedance/gopkg v0.1.3/go.mod h1:576VvJ+eJgyCzdjS+c4+77QF3p7ubbtiKARP3TxducM=
+github.com/bytedance/sonic v1.15.0 h1:/PXeWFaR5ElNcVE84U0dOHjiMHQOwNIx3K4ymzh/uSE=
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+github.com/bytedance/sonic/loader v0.5.0 h1:gXH3KVnatgY7loH5/TkeVyXPfESoqSBSBEiDd5VjlgE=
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+github.com/cenkalti/backoff/v4 v4.3.0 h1:MyRJ/UdXutAwSAT+s3wNd7MfTIcy71VQueUuFK343L8=
+github.com/cenkalti/backoff/v4 v4.3.0/go.mod h1:Y3VNntkOUPxTVeUxJ/G5vcM//AlwfmyYozVcomhLiZE=
+github.com/cenkalti/backoff/v5 v5.0.3 h1:ZN+IMa753KfX5hd8vVaMixjnqRZ3y8CuJKRKj1xcsSM=
+github.com/cenkalti/backoff/v5 v5.0.3/go.mod h1:rkhZdG3JZukswDf7f0cwqPNk4K0sa+F97BxZthm/crw=
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+github.com/cloudwego/base64x v0.1.6 h1:t11wG9AECkCDk5fMSoxmufanudBtJ+/HemLstXDLI2M=
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+github.com/creack/pty v1.1.18/go.mod h1:MOBLtS5ELjhRRrroQr9kyvTxUAFNvYEK993ew/Vr4O4=
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backend/internal/config/config.go

@@ -0,0 +1,147 @@
+package config
+
+import (
+	"errors"
+	"fmt"
+	"os"
+	"strconv"
+	"time"
+
+	"github.com/joho/godotenv"
+)
+
+// Config holds all application configuration loaded from environment variables.
+type Config struct {
+	// Server
+	ListenAddr    string
+	JWTSecret     string
+	JWTAccessTTL  time.Duration
+	JWTRefreshTTL time.Duration
+
+	// Initial admin bootstrap (applied on startup if the user does not exist)
+	AdminUsername string
+	AdminPassword string
+
+	// Database
+	DatabaseURL string
+
+	// Storage
+	FilesPath       string
+	ThumbsCachePath string
+	MaxUploadBytes  int64 // reject uploads larger than this (bytes)
+
+	// Thumbnails
+	ThumbWidth    int
+	ThumbHeight   int
+	PreviewWidth  int
+	PreviewHeight int
+	// ThumbMaxPixels caps the pixel count of a source image decoded in-process by
+	// the pure-Go fallback (a decompression-bomb guard and memory bound); larger
+	// images then get a placeholder. It does not apply when vipsthumbnail is
+	// installed, which shrinks on load regardless of source size.
+	ThumbMaxPixels int
+	// ThumbConcurrency bounds how many thumbnails/previews are generated at once,
+	// so a burst of large images can't saturate every core or exhaust RAM. 0 =
+	// auto (half the available CPUs).
+	ThumbConcurrency int
+
+	// Import
+	ImportPath string
+
+	// Static SPA. When set, the server serves the built frontend (and falls
+	// back to index.html for client routes) on the same port as the API. Empty
+	// in local development, where the Vite dev server serves the UI separately.
+	StaticDir string
+}
+
+// Load reads a .env file (if present) then loads all configuration from
+// environment variables. Returns an error listing every missing or invalid var.
+func Load() (*Config, error) {
+	// Non-fatal: .env may not exist in production.
+	_ = godotenv.Load()
+
+	var errs []error
+
+	requireStr := func(key string) string {
+		v := os.Getenv(key)
+		if v == "" {
+			errs = append(errs, fmt.Errorf("%s is required", key))
+		}
+		return v
+	}
+
+	defaultStr := func(key, def string) string {
+		if v := os.Getenv(key); v != "" {
+			return v
+		}
+		return def
+	}
+
+	parseDuration := func(key, def string) time.Duration {
+		raw := defaultStr(key, def)
+		d, err := time.ParseDuration(raw)
+		if err != nil {
+			errs = append(errs, fmt.Errorf("%s: invalid duration %q: %w", key, raw, err))
+			return 0
+		}
+		return d
+	}
+
+	parseInt := func(key string, def int) int {
+		raw := os.Getenv(key)
+		if raw == "" {
+			return def
+		}
+		n, err := strconv.Atoi(raw)
+		if err != nil {
+			errs = append(errs, fmt.Errorf("%s: invalid integer %q: %w", key, raw, err))
+			return def
+		}
+		return n
+	}
+
+	parseInt64 := func(key string, def int64) int64 {
+		raw := os.Getenv(key)
+		if raw == "" {
+			return def
+		}
+		n, err := strconv.ParseInt(raw, 10, 64)
+		if err != nil {
+			errs = append(errs, fmt.Errorf("%s: invalid integer %q: %w", key, raw, err))
+			return def
+		}
+		return n
+	}
+
+	cfg := &Config{
+		ListenAddr:    defaultStr("LISTEN_ADDR", ":42776"),
+		JWTSecret:     requireStr("JWT_SECRET"),
+		JWTAccessTTL:  parseDuration("JWT_ACCESS_TTL", "15m"),
+		JWTRefreshTTL: parseDuration("JWT_REFRESH_TTL", "720h"),
+
+		AdminUsername: defaultStr("ADMIN_USERNAME", "admin"),
+		AdminPassword: requireStr("ADMIN_PASSWORD"),
+
+		DatabaseURL: requireStr("DATABASE_URL"),
+
+		FilesPath:       requireStr("FILES_PATH"),
+		ThumbsCachePath: requireStr("THUMBS_CACHE_PATH"),
+		MaxUploadBytes:  parseInt64("MAX_UPLOAD_BYTES", 500<<20), // 500 MiB
+
+		ThumbWidth:       parseInt("THUMB_WIDTH", 160),
+		ThumbHeight:      parseInt("THUMB_HEIGHT", 160),
+		PreviewWidth:     parseInt("PREVIEW_WIDTH", 1920),
+		PreviewHeight:    parseInt("PREVIEW_HEIGHT", 1080),
+		ThumbMaxPixels:   parseInt("THUMB_MAX_PIXELS", 300_000_000), // ~300 Mpx (e.g. 13000×17000)
+		ThumbConcurrency: parseInt("THUMB_CONCURRENCY", 0),          // 0 = auto
+
+		ImportPath: requireStr("IMPORT_PATH"),
+
+		StaticDir: defaultStr("STATIC_DIR", ""),
+	}
+
+	if len(errs) > 0 {
+		return nil, errors.Join(errs...)
+	}
+	return cfg, nil
+}

backend/internal/db/db.go

@@ -0,0 +1,70 @@
+// Package db provides shared helpers used by all database adapters.
+package db
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
+)
+
+// txKey is the context key used to store an active transaction.
+type txKey struct{}
+
+// TxFromContext returns the pgx.Tx stored in ctx by the Transactor, along
+// with a boolean indicating whether a transaction is active.
+func TxFromContext(ctx context.Context) (pgx.Tx, bool) {
+	tx, ok := ctx.Value(txKey{}).(pgx.Tx)
+	return tx, ok
+}
+
+// ContextWithTx returns a copy of ctx that carries tx.
+// Called by the Transactor before invoking the user function.
+func ContextWithTx(ctx context.Context, tx pgx.Tx) context.Context {
+	return context.WithValue(ctx, txKey{}, tx)
+}
+
+// Querier is the common query interface satisfied by both *pgxpool.Pool and
+// pgx.Tx, allowing repo helpers to work with either.
+type Querier interface {
+	QueryRow(ctx context.Context, sql string, args ...any) pgx.Row
+	Query(ctx context.Context, sql string, args ...any) (pgx.Rows, error)
+	Exec(ctx context.Context, sql string, args ...any) (pgconn.CommandTag, error)
+}
+
+// ScanRow executes a single-row query against q and scans the result using
+// scan. It wraps pgx.ErrNoRows so callers can detect missing rows without
+// importing pgx directly.
+func ScanRow[T any](ctx context.Context, q Querier, sql string, args []any, scan func(pgx.Row) (T, error)) (T, error) {
+	row := q.QueryRow(ctx, sql, args...)
+	val, err := scan(row)
+	if err != nil {
+		var zero T
+		if err == pgx.ErrNoRows {
+			return zero, fmt.Errorf("%w", pgx.ErrNoRows)
+		}
+		return zero, fmt.Errorf("ScanRow: %w", err)
+	}
+	return val, nil
+}
+
+// ClampLimit enforces the [1, max] range on limit, returning def when limit
+// is zero or negative.
+func ClampLimit(limit, def, max int) int {
+	if limit <= 0 {
+		return def
+	}
+	if limit > max {
+		return max
+	}
+	return limit
+}
+
+// ClampOffset returns 0 for negative offsets.
+func ClampOffset(offset int) int {
+	if offset < 0 {
+		return 0
+	}
+	return offset
+}

backend/internal/db/postgres/acl_repo.go

@@ -0,0 +1,118 @@
+package postgres
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+type permissionRow struct {
+	UserID       int16     `db:"user_id"`
+	UserName     string    `db:"user_name"`
+	ObjectTypeID int16     `db:"object_type_id"`
+	ObjectID     uuid.UUID `db:"object_id"`
+	CanView      bool      `db:"can_view"`
+	CanEdit      bool      `db:"can_edit"`
+}
+
+func toPermission(r permissionRow) domain.Permission {
+	return domain.Permission{
+		UserID:       r.UserID,
+		UserName:     r.UserName,
+		ObjectTypeID: r.ObjectTypeID,
+		ObjectID:     r.ObjectID,
+		CanView:      r.CanView,
+		CanEdit:      r.CanEdit,
+	}
+}
+
+// ACLRepo implements port.ACLRepo using PostgreSQL.
+type ACLRepo struct {
+	pool *pgxpool.Pool
+}
+
+// NewACLRepo creates an ACLRepo backed by pool.
+func NewACLRepo(pool *pgxpool.Pool) *ACLRepo {
+	return &ACLRepo{pool: pool}
+}
+
+var _ port.ACLRepo = (*ACLRepo)(nil)
+
+func (r *ACLRepo) List(ctx context.Context, objectTypeID int16, objectID uuid.UUID) ([]domain.Permission, error) {
+	const sql = `
+		SELECT p.user_id, u.name AS user_name, p.object_type_id, p.object_id,
+		       p.can_view, p.can_edit
+		FROM acl.permissions p
+		JOIN core.users u ON u.id = p.user_id
+		WHERE p.object_type_id = $1 AND p.object_id = $2
+		ORDER BY u.name`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql, objectTypeID, objectID)
+	if err != nil {
+		return nil, fmt.Errorf("ACLRepo.List: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[permissionRow])
+	if err != nil {
+		return nil, fmt.Errorf("ACLRepo.List scan: %w", err)
+	}
+	perms := make([]domain.Permission, len(collected))
+	for i, row := range collected {
+		perms[i] = toPermission(row)
+	}
+	return perms, nil
+}
+
+func (r *ACLRepo) Get(ctx context.Context, userID int16, objectTypeID int16, objectID uuid.UUID) (*domain.Permission, error) {
+	const sql = `
+		SELECT p.user_id, u.name AS user_name, p.object_type_id, p.object_id,
+		       p.can_view, p.can_edit
+		FROM acl.permissions p
+		JOIN core.users u ON u.id = p.user_id
+		WHERE p.user_id = $1 AND p.object_type_id = $2 AND p.object_id = $3`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql, userID, objectTypeID, objectID)
+	if err != nil {
+		return nil, fmt.Errorf("ACLRepo.Get: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[permissionRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("ACLRepo.Get scan: %w", err)
+	}
+	p := toPermission(row)
+	return &p, nil
+}
+
+func (r *ACLRepo) Set(ctx context.Context, objectTypeID int16, objectID uuid.UUID, perms []domain.Permission) error {
+	q := connOrTx(ctx, r.pool)
+
+	const del = `DELETE FROM acl.permissions WHERE object_type_id = $1 AND object_id = $2`
+	if _, err := q.Exec(ctx, del, objectTypeID, objectID); err != nil {
+		return fmt.Errorf("ACLRepo.Set delete: %w", err)
+	}
+
+	if len(perms) == 0 {
+		return nil
+	}
+
+	const ins = `
+		INSERT INTO acl.permissions (user_id, object_type_id, object_id, can_view, can_edit)
+		VALUES ($1, $2, $3, $4, $5)`
+	for _, p := range perms {
+		if _, err := q.Exec(ctx, ins, p.UserID, objectTypeID, objectID, p.CanView, p.CanEdit); err != nil {
+			return fmt.Errorf("ACLRepo.Set insert: %w", err)
+		}
+	}
+	return nil
+}

backend/internal/db/postgres/audit_repo.go

@@ -0,0 +1,169 @@
+package postgres
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"tanabata/backend/internal/db"
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+// auditRowWithTotal matches the columns returned by the audit log SELECT.
+// object_type is nullable (LEFT JOIN), object_id and details are nullable columns.
+type auditRowWithTotal struct {
+	ID          int64           `db:"id"`
+	UserID      int16           `db:"user_id"`
+	UserName    string          `db:"user_name"`
+	Action      string          `db:"action"`
+	ObjectType  *string         `db:"object_type"`
+	ObjectID    *uuid.UUID      `db:"object_id"`
+	Details     json.RawMessage `db:"details"`
+	PerformedAt time.Time       `db:"performed_at"`
+	Total       int             `db:"total"`
+}
+
+func toAuditEntry(r auditRowWithTotal) domain.AuditEntry {
+	return domain.AuditEntry{
+		ID:          r.ID,
+		UserID:      r.UserID,
+		UserName:    r.UserName,
+		Action:      r.Action,
+		ObjectType:  r.ObjectType,
+		ObjectID:    r.ObjectID,
+		Details:     r.Details,
+		PerformedAt: r.PerformedAt,
+	}
+}
+
+// AuditRepo implements port.AuditRepo using PostgreSQL.
+type AuditRepo struct {
+	pool *pgxpool.Pool
+}
+
+// NewAuditRepo creates an AuditRepo backed by pool.
+func NewAuditRepo(pool *pgxpool.Pool) *AuditRepo {
+	return &AuditRepo{pool: pool}
+}
+
+var _ port.AuditRepo = (*AuditRepo)(nil)
+
+// Log inserts one audit record. action_type_id and object_type_id are resolved
+// from the reference tables inside the INSERT via subqueries.
+func (r *AuditRepo) Log(ctx context.Context, entry domain.AuditEntry) error {
+	const sql = `
+		INSERT INTO activity.audit_log
+		    (user_id, action_type_id, object_type_id, object_id, details)
+		VALUES (
+		    $1,
+		    (SELECT id FROM activity.action_types WHERE name = $2),
+		    CASE WHEN $3::text IS NOT NULL
+		         THEN (SELECT id FROM core.object_types WHERE name = $3)
+		         ELSE NULL END,
+		    $4,
+		    $5
+		)`
+
+	q := connOrTx(ctx, r.pool)
+	_, err := q.Exec(ctx, sql,
+		entry.UserID,
+		entry.Action,
+		entry.ObjectType,
+		entry.ObjectID,
+		entry.Details,
+	)
+	if err != nil {
+		return fmt.Errorf("AuditRepo.Log: %w", err)
+	}
+	return nil
+}
+
+// List returns a filtered, offset-paginated page of audit log entries ordered
+// newest-first.
+func (r *AuditRepo) List(ctx context.Context, filter domain.AuditFilter) (*domain.AuditPage, error) {
+	var conds []string
+	args := make([]any, 0, 8)
+	n := 1
+
+	if filter.UserID != nil {
+		conds = append(conds, fmt.Sprintf("a.user_id = $%d", n))
+		args = append(args, *filter.UserID)
+		n++
+	}
+	if filter.Action != "" {
+		conds = append(conds, fmt.Sprintf("at.name = $%d", n))
+		args = append(args, filter.Action)
+		n++
+	}
+	if filter.ObjectType != "" {
+		conds = append(conds, fmt.Sprintf("ot.name = $%d", n))
+		args = append(args, filter.ObjectType)
+		n++
+	}
+	if filter.ObjectID != nil {
+		conds = append(conds, fmt.Sprintf("a.object_id = $%d", n))
+		args = append(args, *filter.ObjectID)
+		n++
+	}
+	if filter.From != nil {
+		conds = append(conds, fmt.Sprintf("a.performed_at >= $%d", n))
+		args = append(args, *filter.From)
+		n++
+	}
+	if filter.To != nil {
+		conds = append(conds, fmt.Sprintf("a.performed_at <= $%d", n))
+		args = append(args, *filter.To)
+		n++
+	}
+
+	where := ""
+	if len(conds) > 0 {
+		where = "WHERE " + strings.Join(conds, " AND ")
+	}
+
+	limit := db.ClampLimit(filter.Limit, 50, 200)
+	offset := db.ClampOffset(filter.Offset)
+	args = append(args, limit, offset)
+
+	sql := fmt.Sprintf(`
+		SELECT a.id, a.user_id, u.name AS user_name,
+		       at.name AS action,
+		       ot.name AS object_type,
+		       a.object_id, a.details,
+		       a.performed_at,
+		       COUNT(*) OVER() AS total
+		FROM activity.audit_log a
+		JOIN  core.users u             ON u.id  = a.user_id
+		JOIN  activity.action_types at ON at.id = a.action_type_id
+		LEFT JOIN core.object_types ot ON ot.id = a.object_type_id
+		%s
+		ORDER BY a.performed_at DESC
+		LIMIT $%d OFFSET $%d`, where, n, n+1)
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql, args...)
+	if err != nil {
+		return nil, fmt.Errorf("AuditRepo.List: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[auditRowWithTotal])
+	if err != nil {
+		return nil, fmt.Errorf("AuditRepo.List scan: %w", err)
+	}
+
+	page := &domain.AuditPage{Offset: offset, Limit: limit}
+	if len(collected) > 0 {
+		page.Total = collected[0].Total
+	}
+	page.Items = make([]domain.AuditEntry, len(collected))
+	for i, row := range collected {
+		page.Items[i] = toAuditEntry(row)
+	}
+	return page, nil
+}

backend/internal/db/postgres/category_repo.go

@@ -0,0 +1,303 @@
+package postgres
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+// ---------------------------------------------------------------------------
+// Row struct
+// ---------------------------------------------------------------------------
+
+type categoryRow struct {
+	ID          uuid.UUID `db:"id"`
+	Name        string    `db:"name"`
+	Notes       *string   `db:"notes"`
+	Color       *string   `db:"color"`
+	Metadata    []byte    `db:"metadata"`
+	CreatorID   int16     `db:"creator_id"`
+	CreatorName string    `db:"creator_name"`
+	IsPublic    bool      `db:"is_public"`
+}
+
+type categoryRowWithTotal struct {
+	categoryRow
+	Total int `db:"total"`
+}
+
+// ---------------------------------------------------------------------------
+// Converter
+// ---------------------------------------------------------------------------
+
+func toCategory(r categoryRow) domain.Category {
+	c := domain.Category{
+		ID:          r.ID,
+		Name:        r.Name,
+		Notes:       r.Notes,
+		Color:       r.Color,
+		CreatorID:   r.CreatorID,
+		CreatorName: r.CreatorName,
+		IsPublic:    r.IsPublic,
+		CreatedAt:   domain.UUIDCreatedAt(r.ID),
+	}
+	if len(r.Metadata) > 0 && string(r.Metadata) != "null" {
+		c.Metadata = json.RawMessage(r.Metadata)
+	}
+	return c
+}
+
+// ---------------------------------------------------------------------------
+// Shared SQL
+// ---------------------------------------------------------------------------
+
+const categorySelectFrom = `
+SELECT
+    c.id,
+    c.name,
+    c.notes,
+    c.color,
+    c.metadata,
+    c.creator_id,
+    u.name AS creator_name,
+    c.is_public
+FROM data.categories c
+JOIN core.users u ON u.id = c.creator_id`
+
+func categorySortColumn(s string) string {
+	if s == "name" {
+		return "c.name"
+	}
+	return "c.id" // "created"
+}
+
+// ---------------------------------------------------------------------------
+// CategoryRepo — implements port.CategoryRepo
+// ---------------------------------------------------------------------------
+
+// CategoryRepo handles category CRUD using PostgreSQL.
+type CategoryRepo struct {
+	pool *pgxpool.Pool
+}
+
+var _ port.CategoryRepo = (*CategoryRepo)(nil)
+
+// NewCategoryRepo creates a CategoryRepo backed by pool.
+func NewCategoryRepo(pool *pgxpool.Pool) *CategoryRepo {
+	return &CategoryRepo{pool: pool}
+}
+
+// ---------------------------------------------------------------------------
+// List
+// ---------------------------------------------------------------------------
+
+func (r *CategoryRepo) List(ctx context.Context, params port.OffsetParams) (*domain.CategoryOffsetPage, error) {
+	order := "ASC"
+	if strings.ToLower(params.Order) == "desc" {
+		order = "DESC"
+	}
+	sortCol := categorySortColumn(params.Sort)
+
+	args := []any{}
+	n := 1
+	var conditions []string
+
+	if params.Search != "" {
+		conditions = append(conditions, fmt.Sprintf("lower(c.name) LIKE lower($%d)", n))
+		args = append(args, "%"+params.Search+"%")
+		n++
+	}
+	// Restrict to categories the viewer may see (private-by-default), unless admin.
+	if !params.ViewerIsAdmin {
+		var aclCond string
+		aclCond, n, args = aclVisibilityCond("c", objTypeCategory, params.ViewerID, n, args)
+		conditions = append(conditions, aclCond)
+	}
+
+	where := ""
+	if len(conditions) > 0 {
+		where = "WHERE " + strings.Join(conditions, " AND ")
+	}
+
+	limit := params.Limit
+	if limit <= 0 {
+		limit = 50
+	}
+	offset := params.Offset
+	if offset < 0 {
+		offset = 0
+	}
+
+	query := fmt.Sprintf(`
+SELECT
+    c.id, c.name, c.notes, c.color, c.metadata,
+    c.creator_id, u.name AS creator_name, c.is_public,
+    COUNT(*) OVER() AS total
+FROM data.categories c
+JOIN core.users u ON u.id = c.creator_id
+%s
+ORDER BY %s %s NULLS LAST, c.id ASC
+LIMIT $%d OFFSET $%d`, where, sortCol, order, n, n+1)
+
+	args = append(args, limit, offset)
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query, args...)
+	if err != nil {
+		return nil, fmt.Errorf("CategoryRepo.List query: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[categoryRowWithTotal])
+	if err != nil {
+		return nil, fmt.Errorf("CategoryRepo.List scan: %w", err)
+	}
+
+	items := make([]domain.Category, len(collected))
+	total := 0
+	for i, row := range collected {
+		items[i] = toCategory(row.categoryRow)
+		total = row.Total
+	}
+	return &domain.CategoryOffsetPage{
+		Items:  items,
+		Total:  total,
+		Offset: offset,
+		Limit:  limit,
+	}, nil
+}
+
+// ---------------------------------------------------------------------------
+// GetByID
+// ---------------------------------------------------------------------------
+
+func (r *CategoryRepo) GetByID(ctx context.Context, id uuid.UUID) (*domain.Category, error) {
+	const query = categorySelectFrom + `
+WHERE c.id = $1`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query, id)
+	if err != nil {
+		return nil, fmt.Errorf("CategoryRepo.GetByID: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[categoryRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("CategoryRepo.GetByID scan: %w", err)
+	}
+	c := toCategory(row)
+	return &c, nil
+}
+
+// ---------------------------------------------------------------------------
+// Create
+// ---------------------------------------------------------------------------
+
+func (r *CategoryRepo) Create(ctx context.Context, c *domain.Category) (*domain.Category, error) {
+	const query = `
+WITH ins AS (
+    INSERT INTO data.categories (name, notes, color, metadata, creator_id, is_public)
+    VALUES ($1, $2, $3, $4, $5, $6)
+    RETURNING *
+)
+SELECT ins.id, ins.name, ins.notes, ins.color, ins.metadata,
+       ins.creator_id, u.name AS creator_name, ins.is_public
+FROM ins
+JOIN core.users u ON u.id = ins.creator_id`
+
+	var meta any
+	if len(c.Metadata) > 0 {
+		meta = c.Metadata
+	}
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query,
+		c.Name, c.Notes, c.Color, meta, c.CreatorID, c.IsPublic)
+	if err != nil {
+		return nil, fmt.Errorf("CategoryRepo.Create: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[categoryRow])
+	if err != nil {
+		if isPgUniqueViolation(err) {
+			return nil, domain.ErrConflict
+		}
+		return nil, fmt.Errorf("CategoryRepo.Create scan: %w", err)
+	}
+	created := toCategory(row)
+	return &created, nil
+}
+
+// ---------------------------------------------------------------------------
+// Update
+// ---------------------------------------------------------------------------
+
+// Update replaces all mutable fields. The caller must merge current values
+// with the patch before calling (read-then-write semantics).
+func (r *CategoryRepo) Update(ctx context.Context, id uuid.UUID, c *domain.Category) (*domain.Category, error) {
+	const query = `
+WITH upd AS (
+    UPDATE data.categories SET
+        name      = $2,
+        notes     = $3,
+        color     = $4,
+        metadata  = COALESCE($5, metadata),
+        is_public = $6
+    WHERE id = $1
+    RETURNING *
+)
+SELECT upd.id, upd.name, upd.notes, upd.color, upd.metadata,
+       upd.creator_id, u.name AS creator_name, upd.is_public
+FROM upd
+JOIN core.users u ON u.id = upd.creator_id`
+
+	var meta any
+	if len(c.Metadata) > 0 {
+		meta = c.Metadata
+	}
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query,
+		id, c.Name, c.Notes, c.Color, meta, c.IsPublic)
+	if err != nil {
+		return nil, fmt.Errorf("CategoryRepo.Update: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[categoryRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		if isPgUniqueViolation(err) {
+			return nil, domain.ErrConflict
+		}
+		return nil, fmt.Errorf("CategoryRepo.Update scan: %w", err)
+	}
+	updated := toCategory(row)
+	return &updated, nil
+}
+
+// ---------------------------------------------------------------------------
+// Delete
+// ---------------------------------------------------------------------------
+
+func (r *CategoryRepo) Delete(ctx context.Context, id uuid.UUID) error {
+	const query = `DELETE FROM data.categories WHERE id = $1`
+
+	q := connOrTx(ctx, r.pool)
+	ct, err := q.Exec(ctx, query, id)
+	if err != nil {
+		return fmt.Errorf("CategoryRepo.Delete: %w", err)
+	}
+	if ct.RowsAffected() == 0 {
+		return domain.ErrNotFound
+	}
+	return nil
+}

backend/internal/db/postgres/file_repo.go

@@ -0,0 +1,843 @@
+package postgres
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"tanabata/backend/internal/db"
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+// ---------------------------------------------------------------------------
+// Row structs
+// ---------------------------------------------------------------------------
+
+type fileRow struct {
+	ID              uuid.UUID       `db:"id"`
+	OriginalName    *string         `db:"original_name"`
+	MIMEType        string          `db:"mime_type"`
+	MIMEExtension   string          `db:"mime_extension"`
+	ContentDatetime time.Time       `db:"content_datetime"`
+	Notes           *string         `db:"notes"`
+	Metadata        json.RawMessage `db:"metadata"`
+	EXIF            json.RawMessage `db:"exif"`
+	PHash           *int64          `db:"phash"`
+	CreatorID       int16           `db:"creator_id"`
+	CreatorName     string          `db:"creator_name"`
+	IsPublic        bool            `db:"is_public"`
+	IsDeleted       bool            `db:"is_deleted"`
+}
+
+// fileTagRow is used for both single-file and batch tag loading.
+// file_id is always selected so the same struct works for both cases.
+type fileTagRow struct {
+	FileID        uuid.UUID       `db:"file_id"`
+	ID            uuid.UUID       `db:"id"`
+	Name          string          `db:"name"`
+	Notes         *string         `db:"notes"`
+	Color         *string         `db:"color"`
+	CategoryID    *uuid.UUID      `db:"category_id"`
+	CategoryName  *string         `db:"category_name"`
+	CategoryColor *string         `db:"category_color"`
+	Metadata      json.RawMessage `db:"metadata"`
+	CreatorID     int16           `db:"creator_id"`
+	CreatorName   string          `db:"creator_name"`
+	IsPublic      bool            `db:"is_public"`
+}
+
+// anchorValRow holds the sort-column values fetched for an anchor file.
+type anchorValRow struct {
+	ContentDatetime time.Time `db:"content_datetime"`
+	OriginalName    string    `db:"original_name"` // COALESCE(original_name,'') applied in SQL
+	MIMEType        string    `db:"mime_type"`
+}
+
+// ---------------------------------------------------------------------------
+// Converters
+// ---------------------------------------------------------------------------
+
+func toFile(r fileRow) domain.File {
+	return domain.File{
+		ID:              r.ID,
+		OriginalName:    r.OriginalName,
+		MIMEType:        r.MIMEType,
+		MIMEExtension:   r.MIMEExtension,
+		ContentDatetime: r.ContentDatetime,
+		Notes:           r.Notes,
+		Metadata:        r.Metadata,
+		EXIF:            r.EXIF,
+		PHash:           r.PHash,
+		CreatorID:       r.CreatorID,
+		CreatorName:     r.CreatorName,
+		IsPublic:        r.IsPublic,
+		IsDeleted:       r.IsDeleted,
+		CreatedAt:       domain.UUIDCreatedAt(r.ID),
+	}
+}
+
+func toTagFromFileTag(r fileTagRow) domain.Tag {
+	return domain.Tag{
+		ID:            r.ID,
+		Name:          r.Name,
+		Notes:         r.Notes,
+		Color:         r.Color,
+		CategoryID:    r.CategoryID,
+		CategoryName:  r.CategoryName,
+		CategoryColor: r.CategoryColor,
+		Metadata:      r.Metadata,
+		CreatorID:     r.CreatorID,
+		CreatorName:   r.CreatorName,
+		IsPublic:      r.IsPublic,
+		CreatedAt:     domain.UUIDCreatedAt(r.ID),
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Cursor
+// ---------------------------------------------------------------------------
+
+type fileCursor struct {
+	Sort  string `json:"s"`  // canonical sort name
+	Order string `json:"o"`  // "ASC" or "DESC"
+	ID    string `json:"id"` // UUID of the boundary file
+	Val   string `json:"v"`  // sort column value; empty for "created" (id IS the key)
+}
+
+func encodeCursor(c fileCursor) string {
+	b, _ := json.Marshal(c)
+	return base64.RawURLEncoding.EncodeToString(b)
+}
+
+func decodeCursor(s string) (fileCursor, error) {
+	b, err := base64.RawURLEncoding.DecodeString(s)
+	if err != nil {
+		return fileCursor{}, fmt.Errorf("cursor: invalid encoding")
+	}
+	var c fileCursor
+	if err := json.Unmarshal(b, &c); err != nil {
+		return fileCursor{}, fmt.Errorf("cursor: invalid format")
+	}
+	return c, nil
+}
+
+// makeCursor builds a fileCursor from a boundary row and the current sort/order.
+func makeCursor(r fileRow, sort, order string) fileCursor {
+	var val string
+	switch sort {
+	case "content_datetime":
+		val = r.ContentDatetime.UTC().Format(time.RFC3339Nano)
+	case "original_name":
+		if r.OriginalName != nil {
+			val = *r.OriginalName
+		}
+	case "mime":
+		val = r.MIMEType
+		// "created": val is empty; f.id is the sort key.
+	}
+	return fileCursor{Sort: sort, Order: order, ID: r.ID.String(), Val: val}
+}
+
+// ---------------------------------------------------------------------------
+// Sort helpers
+// ---------------------------------------------------------------------------
+
+func normSort(s string) string {
+	switch s {
+	case "content_datetime", "original_name", "mime":
+		return s
+	default:
+		return "created"
+	}
+}
+
+func normOrder(o string) string {
+	if strings.EqualFold(o, "asc") {
+		return "ASC"
+	}
+	return "DESC"
+}
+
+// buildKeysetCond returns a keyset WHERE fragment and an ORDER BY fragment.
+//
+//   - forward=true:  items after the cursor in the sort order (standard next-page)
+//   - forward=false: items before the cursor (previous-page); ORDER BY is reversed,
+//     caller must reverse the result slice after fetching
+//   - incl=true: include the cursor file itself (anchor case; uses ≤ / ≥)
+//
+// All user values are bound as parameters — no SQL injection possible.
+func buildKeysetCond(
+	sort, order string,
+	forward, incl bool,
+	cursorID uuid.UUID, cursorVal string,
+	n int, args []any,
+) (where, orderBy string, nextN int, outArgs []any) {
+	// goDown=true → want smaller values → primary comparison is "<".
+	// Applies for DESC+forward and ASC+backward.
+	goDown := (order == "DESC") == forward
+
+	var op, idOp string
+	if goDown {
+		op = "<"
+		if incl {
+			idOp = "<="
+		} else {
+			idOp = "<"
+		}
+	} else {
+		op = ">"
+		if incl {
+			idOp = ">="
+		} else {
+			idOp = ">"
+		}
+	}
+
+	// Effective ORDER BY direction: reversed for backward so the DB returns
+	// the closest items first (the ones we keep after trimming the extra).
+	dir := order
+	if !forward {
+		if order == "DESC" {
+			dir = "ASC"
+		} else {
+			dir = "DESC"
+		}
+	}
+
+	switch sort {
+	case "created":
+		// Single-column keyset: f.id (UUID v7, so ordering = chronological).
+		where = fmt.Sprintf("f.id %s $%d", idOp, n)
+		orderBy = fmt.Sprintf("f.id %s", dir)
+		outArgs = append(args, cursorID)
+		n++
+
+	case "content_datetime":
+		// Two-column keyset: (content_datetime, id).
+		// $n is referenced twice in the SQL (< and =) but passed once in args —
+		// PostgreSQL extended protocol allows multiple references to $N.
+		t, _ := time.Parse(time.RFC3339Nano, cursorVal)
+		where = fmt.Sprintf(
+			"(f.content_datetime %s $%d OR (f.content_datetime = $%d AND f.id %s $%d))",
+			op, n, n, idOp, n+1)
+		orderBy = fmt.Sprintf("f.content_datetime %s, f.id %s", dir, dir)
+		outArgs = append(args, t, cursorID)
+		n += 2
+
+	case "original_name":
+		// COALESCE treats NULL names as '' for stable pagination.
+		where = fmt.Sprintf(
+			"(COALESCE(f.original_name,'') %s $%d OR (COALESCE(f.original_name,'') = $%d AND f.id %s $%d))",
+			op, n, n, idOp, n+1)
+		orderBy = fmt.Sprintf("COALESCE(f.original_name,'') %s, f.id %s", dir, dir)
+		outArgs = append(args, cursorVal, cursorID)
+		n += 2
+
+	default: // "mime"
+		where = fmt.Sprintf(
+			"(mt.name %s $%d OR (mt.name = $%d AND f.id %s $%d))",
+			op, n, n, idOp, n+1)
+		orderBy = fmt.Sprintf("mt.name %s, f.id %s", dir, dir)
+		outArgs = append(args, cursorVal, cursorID)
+		n += 2
+	}
+
+	nextN = n
+	return
+}
+
+// defaultOrderBy returns the natural ORDER BY for the first page (no cursor).
+func defaultOrderBy(sort, order string) string {
+	switch sort {
+	case "created":
+		return fmt.Sprintf("f.id %s", order)
+	case "content_datetime":
+		return fmt.Sprintf("f.content_datetime %s, f.id %s", order, order)
+	case "original_name":
+		return fmt.Sprintf("COALESCE(f.original_name,'') %s, f.id %s", order, order)
+	default: // "mime"
+		return fmt.Sprintf("mt.name %s, f.id %s", order, order)
+	}
+}
+
+// ---------------------------------------------------------------------------
+// FileRepo
+// ---------------------------------------------------------------------------
+
+// FileRepo implements port.FileRepo using PostgreSQL.
+type FileRepo struct {
+	pool *pgxpool.Pool
+}
+
+// NewFileRepo creates a FileRepo backed by pool.
+func NewFileRepo(pool *pgxpool.Pool) *FileRepo {
+	return &FileRepo{pool: pool}
+}
+
+var _ port.FileRepo = (*FileRepo)(nil)
+
+// fileSelectCTE is the SELECT appended after a CTE named "r" that exposes
+// all file columns (including mime_id). Used by Create, Update, and Restore
+// to get the full denormalized record in a single round-trip.
+const fileSelectCTE = `
+    SELECT r.id, r.original_name,
+           mt.name AS mime_type, mt.extension AS mime_extension,
+           r.content_datetime, r.notes, r.metadata, r.exif, r.phash,
+           r.creator_id, u.name AS creator_name,
+           r.is_public, r.is_deleted
+    FROM r
+    JOIN core.mime_types mt ON mt.id = r.mime_id
+    JOIN core.users u       ON u.id  = r.creator_id`
+
+// ---------------------------------------------------------------------------
+// Create
+// ---------------------------------------------------------------------------
+
+// Create inserts a new file record using the ID already set on f.
+// The MIME type is resolved from f.MIMEType (name string) via a subquery.
+func (r *FileRepo) Create(ctx context.Context, f *domain.File) (*domain.File, error) {
+	const sqlStr = `
+        WITH r AS (
+            INSERT INTO data.files
+                (id, original_name, mime_id, content_datetime, notes, metadata, exif, phash, creator_id, is_public)
+            VALUES (
+                $1,
+                $2,
+                (SELECT id FROM core.mime_types WHERE name = $3),
+                $4, $5, $6, $7, $8, $9, $10
+            )
+            RETURNING id, original_name, mime_id, content_datetime, notes,
+                      metadata, exif, phash, creator_id, is_public, is_deleted
+        )` + fileSelectCTE
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sqlStr,
+		f.ID, f.OriginalName, f.MIMEType, f.ContentDatetime,
+		f.Notes, f.Metadata, f.EXIF, f.PHash,
+		f.CreatorID, f.IsPublic,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("FileRepo.Create: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[fileRow])
+	if err != nil {
+		return nil, fmt.Errorf("FileRepo.Create scan: %w", err)
+	}
+	created := toFile(row)
+	return &created, nil
+}
+
+// ---------------------------------------------------------------------------
+// GetByID
+// ---------------------------------------------------------------------------
+
+func (r *FileRepo) GetByID(ctx context.Context, id uuid.UUID) (*domain.File, error) {
+	const sqlStr = `
+        SELECT f.id, f.original_name,
+               mt.name AS mime_type, mt.extension AS mime_extension,
+               f.content_datetime, f.notes, f.metadata, f.exif, f.phash,
+               f.creator_id, u.name AS creator_name,
+               f.is_public, f.is_deleted
+        FROM data.files f
+        JOIN core.mime_types mt ON mt.id = f.mime_id
+        JOIN core.users u       ON u.id  = f.creator_id
+        WHERE f.id = $1`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sqlStr, id)
+	if err != nil {
+		return nil, fmt.Errorf("FileRepo.GetByID: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[fileRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("FileRepo.GetByID scan: %w", err)
+	}
+	f := toFile(row)
+	tags, err := r.ListTags(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	f.Tags = tags
+	return &f, nil
+}
+
+// ---------------------------------------------------------------------------
+// Update
+// ---------------------------------------------------------------------------
+
+// Update applies editable metadata fields. MIME type and EXIF are immutable.
+func (r *FileRepo) Update(ctx context.Context, id uuid.UUID, f *domain.File) (*domain.File, error) {
+	const sqlStr = `
+        WITH r AS (
+            UPDATE data.files
+            SET original_name    = $2,
+                content_datetime = $3,
+                notes            = $4,
+                metadata         = $5,
+                is_public        = $6
+            WHERE id = $1
+            RETURNING id, original_name, mime_id, content_datetime, notes,
+                      metadata, exif, phash, creator_id, is_public, is_deleted
+        )` + fileSelectCTE
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sqlStr,
+		id, f.OriginalName, f.ContentDatetime,
+		f.Notes, f.Metadata, f.IsPublic,
+	)
+	if err != nil {
+		return nil, fmt.Errorf("FileRepo.Update: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[fileRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("FileRepo.Update scan: %w", err)
+	}
+	updated := toFile(row)
+	tags, err := r.ListTags(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	updated.Tags = tags
+	return &updated, nil
+}
+
+// ---------------------------------------------------------------------------
+// SoftDelete / Restore / DeletePermanent
+// ---------------------------------------------------------------------------
+
+// SoftDelete moves a file to trash (is_deleted = true). Returns ErrNotFound
+// if the file does not exist or is already in trash.
+func (r *FileRepo) SoftDelete(ctx context.Context, id uuid.UUID) error {
+	const sqlStr = `UPDATE data.files SET is_deleted = true WHERE id = $1 AND is_deleted = false`
+	q := connOrTx(ctx, r.pool)
+	tag, err := q.Exec(ctx, sqlStr, id)
+	if err != nil {
+		return fmt.Errorf("FileRepo.SoftDelete: %w", err)
+	}
+	if tag.RowsAffected() == 0 {
+		return domain.ErrNotFound
+	}
+	return nil
+}
+
+// Restore moves a file out of trash (is_deleted = false). Returns ErrNotFound
+// if the file does not exist or is not in trash.
+func (r *FileRepo) Restore(ctx context.Context, id uuid.UUID) (*domain.File, error) {
+	const sqlStr = `
+        WITH r AS (
+            UPDATE data.files
+            SET is_deleted = false
+            WHERE id = $1 AND is_deleted = true
+            RETURNING id, original_name, mime_id, content_datetime, notes,
+                      metadata, exif, phash, creator_id, is_public, is_deleted
+        )` + fileSelectCTE
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sqlStr, id)
+	if err != nil {
+		return nil, fmt.Errorf("FileRepo.Restore: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[fileRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("FileRepo.Restore scan: %w", err)
+	}
+	restored := toFile(row)
+	tags, err := r.ListTags(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	restored.Tags = tags
+	return &restored, nil
+}
+
+// DeletePermanent removes a file record permanently. Only allowed when the
+// file is already in trash (is_deleted = true).
+func (r *FileRepo) DeletePermanent(ctx context.Context, id uuid.UUID) error {
+	const sqlStr = `DELETE FROM data.files WHERE id = $1 AND is_deleted = true`
+	q := connOrTx(ctx, r.pool)
+	tag, err := q.Exec(ctx, sqlStr, id)
+	if err != nil {
+		return fmt.Errorf("FileRepo.DeletePermanent: %w", err)
+	}
+	if tag.RowsAffected() == 0 {
+		return domain.ErrNotFound
+	}
+	return nil
+}
+
+// ---------------------------------------------------------------------------
+// ListTags / SetTags
+// ---------------------------------------------------------------------------
+
+// ListTags returns all tags assigned to a file, ordered by tag name.
+func (r *FileRepo) ListTags(ctx context.Context, fileID uuid.UUID) ([]domain.Tag, error) {
+	m, err := r.loadTagsBatch(ctx, []uuid.UUID{fileID})
+	if err != nil {
+		return nil, err
+	}
+	return m[fileID], nil
+}
+
+// SetTags replaces all tags on a file (full replace semantics).
+func (r *FileRepo) SetTags(ctx context.Context, fileID uuid.UUID, tagIDs []uuid.UUID) error {
+	q := connOrTx(ctx, r.pool)
+	const del = `DELETE FROM data.file_tag WHERE file_id = $1`
+	if _, err := q.Exec(ctx, del, fileID); err != nil {
+		return fmt.Errorf("FileRepo.SetTags delete: %w", err)
+	}
+	if len(tagIDs) == 0 {
+		return nil
+	}
+	const ins = `INSERT INTO data.file_tag (file_id, tag_id) VALUES ($1, $2)`
+	for _, tagID := range tagIDs {
+		if _, err := q.Exec(ctx, ins, fileID, tagID); err != nil {
+			return fmt.Errorf("FileRepo.SetTags insert: %w", err)
+		}
+	}
+	return nil
+}
+
+// ---------------------------------------------------------------------------
+// List
+// ---------------------------------------------------------------------------
+
+// List returns a cursor-paginated page of files.
+//
+// Pagination is keyset-based for stable performance on large tables.
+// Cursor encodes the sort position; the caller provides direction.
+// Anchor mode centres the result around a specific file UUID.
+func (r *FileRepo) List(ctx context.Context, params domain.FileListParams) (*domain.FilePage, error) {
+	sort := normSort(params.Sort)
+	order := normOrder(params.Order)
+	forward := params.Direction != "backward"
+	limit := db.ClampLimit(params.Limit, 50, 200)
+
+	// --- resolve cursor / anchor ---
+	var (
+		cursorID  uuid.UUID
+		cursorVal string
+		hasCursor bool
+		isAnchor  bool
+	)
+
+	switch {
+	case params.Cursor != "":
+		cur, err := decodeCursor(params.Cursor)
+		if err != nil {
+			return nil, fmt.Errorf("%w: %v", domain.ErrValidation, err)
+		}
+		id, err := uuid.Parse(cur.ID)
+		if err != nil {
+			return nil, domain.ErrValidation
+		}
+		// Lock in the sort/order encoded in the cursor so changing query
+		// parameters mid-session doesn't corrupt pagination.
+		sort = normSort(cur.Sort)
+		order = normOrder(cur.Order)
+		cursorID = id
+		cursorVal = cur.Val
+		hasCursor = true
+
+	case params.Anchor != nil:
+		av, err := r.fetchAnchorVals(ctx, *params.Anchor)
+		if err != nil {
+			return nil, err
+		}
+		cursorID = *params.Anchor
+		switch sort {
+		case "content_datetime":
+			cursorVal = av.ContentDatetime.UTC().Format(time.RFC3339Nano)
+		case "original_name":
+			cursorVal = av.OriginalName
+		case "mime":
+			cursorVal = av.MIMEType
+			// "created": cursorVal stays ""; cursorID is the sort key.
+		}
+		hasCursor = true
+		isAnchor = true
+	}
+
+	// Without a cursor there is no meaningful "backward" direction.
+	if !hasCursor {
+		forward = true
+	}
+
+	// --- build WHERE and ORDER BY ---
+	var conds []string
+	args := make([]any, 0, 8)
+	n := 1
+
+	conds = append(conds, fmt.Sprintf("f.is_deleted = $%d", n))
+	args = append(args, params.Trash)
+	n++
+
+	if params.Search != "" {
+		conds = append(conds, fmt.Sprintf("f.original_name ILIKE $%d", n))
+		args = append(args, "%"+params.Search+"%")
+		n++
+	}
+
+	if params.Filter != "" {
+		filterSQL, nextN, filterArgs, err := ParseFilter(params.Filter, n)
+		if err != nil {
+			return nil, fmt.Errorf("%w: %v", domain.ErrValidation, err)
+		}
+		if filterSQL != "" {
+			conds = append(conds, filterSQL)
+			n = nextN
+			args = append(args, filterArgs...)
+		}
+	}
+
+	// Restrict to files the viewer may see (private-by-default), unless admin.
+	if !params.ViewerIsAdmin {
+		var aclCond string
+		aclCond, n, args = aclVisibilityCond("f", objTypeFile, params.ViewerID, n, args)
+		conds = append(conds, aclCond)
+	}
+
+	var orderBy string
+	if hasCursor {
+		ksWhere, ksOrder, nextN, ksArgs := buildKeysetCond(
+			sort, order, forward, isAnchor, cursorID, cursorVal, n, args)
+		conds = append(conds, ksWhere)
+		n = nextN
+		args = ksArgs
+		orderBy = ksOrder
+	} else {
+		orderBy = defaultOrderBy(sort, order)
+	}
+
+	where := ""
+	if len(conds) > 0 {
+		where = "WHERE " + strings.Join(conds, " AND ")
+	}
+
+	// Fetch one extra row to detect whether more items exist beyond this page.
+	args = append(args, limit+1)
+	sqlStr := fmt.Sprintf(`
+        SELECT f.id, f.original_name,
+               mt.name AS mime_type, mt.extension AS mime_extension,
+               f.content_datetime, f.notes, f.metadata, f.exif, f.phash,
+               f.creator_id, u.name AS creator_name,
+               f.is_public, f.is_deleted
+        FROM data.files f
+        JOIN core.mime_types mt ON mt.id = f.mime_id
+        JOIN core.users u       ON u.id  = f.creator_id
+        %s
+        ORDER BY %s
+        LIMIT $%d`, where, orderBy, n)
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sqlStr, args...)
+	if err != nil {
+		return nil, fmt.Errorf("FileRepo.List: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[fileRow])
+	if err != nil {
+		return nil, fmt.Errorf("FileRepo.List scan: %w", err)
+	}
+
+	// --- trim extra row and reverse for backward ---
+	hasMore := len(collected) > limit
+	if hasMore {
+		collected = collected[:limit]
+	}
+	if !forward {
+		// Results were fetched in reversed ORDER BY; invert to restore the
+		// natural sort order expected by the caller.
+		for i, j := 0, len(collected)-1; i < j; i, j = i+1, j-1 {
+			collected[i], collected[j] = collected[j], collected[i]
+		}
+	}
+
+	// --- assemble page ---
+	page := &domain.FilePage{
+		Items: make([]domain.File, len(collected)),
+	}
+	for i, row := range collected {
+		page.Items[i] = toFile(row)
+	}
+
+	// --- set next/prev cursors ---
+	// next_cursor: navigate further in the forward direction.
+	// prev_cursor: navigate further in the backward direction.
+	if len(collected) > 0 {
+		firstCur := encodeCursor(makeCursor(collected[0], sort, order))
+		lastCur := encodeCursor(makeCursor(collected[len(collected)-1], sort, order))
+
+		if forward {
+			// We only know a prev page exists if we arrived via cursor.
+			if hasCursor {
+				page.PrevCursor = &firstCur
+			}
+			if hasMore {
+				page.NextCursor = &lastCur
+			}
+		} else {
+			// Backward: last item (after reversal) is closest to original cursor.
+			if hasCursor {
+				page.NextCursor = &lastCur
+			}
+			if hasMore {
+				page.PrevCursor = &firstCur
+			}
+		}
+	}
+
+	// --- batch-load tags ---
+	if len(page.Items) > 0 {
+		fileIDs := make([]uuid.UUID, len(page.Items))
+		for i, f := range page.Items {
+			fileIDs[i] = f.ID
+		}
+		tagMap, err := r.loadTagsBatch(ctx, fileIDs)
+		if err != nil {
+			return nil, err
+		}
+		for i, f := range page.Items {
+			page.Items[i].Tags = tagMap[f.ID] // nil becomes []domain.Tag{} via loadTagsBatch
+		}
+	}
+
+	return page, nil
+}
+
+// ---------------------------------------------------------------------------
+// Internal helpers
+// ---------------------------------------------------------------------------
+
+// fetchAnchorVals returns the sort-column values for the given file.
+// Used to set up a cursor when the caller provides an anchor UUID.
+func (r *FileRepo) fetchAnchorVals(ctx context.Context, fileID uuid.UUID) (*anchorValRow, error) {
+	const sqlStr = `
+        SELECT f.content_datetime,
+               COALESCE(f.original_name, '') AS original_name,
+               mt.name AS mime_type
+        FROM data.files f
+        JOIN core.mime_types mt ON mt.id = f.mime_id
+        WHERE f.id = $1`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sqlStr, fileID)
+	if err != nil {
+		return nil, fmt.Errorf("FileRepo.fetchAnchorVals: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[anchorValRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("FileRepo.fetchAnchorVals scan: %w", err)
+	}
+	return &row, nil
+}
+
+// loadTagsBatch fetches tags for multiple files in a single query and returns
+// them as a map keyed by file ID. Every requested file ID appears as a key
+// (with an empty slice if the file has no tags).
+func (r *FileRepo) loadTagsBatch(ctx context.Context, fileIDs []uuid.UUID) (map[uuid.UUID][]domain.Tag, error) {
+	if len(fileIDs) == 0 {
+		return nil, nil
+	}
+
+	// Build a parameterised IN list. The max page size is 200, so at most 200
+	// placeholders — well within PostgreSQL's limits.
+	placeholders := make([]string, len(fileIDs))
+	args := make([]any, len(fileIDs))
+	for i, id := range fileIDs {
+		placeholders[i] = fmt.Sprintf("$%d", i+1)
+		args[i] = id
+	}
+
+	sqlStr := fmt.Sprintf(`
+        SELECT ft.file_id,
+               t.id, t.name, t.notes, t.color,
+               t.category_id,
+               c.name  AS category_name,
+               c.color AS category_color,
+               t.metadata, t.creator_id, u.name AS creator_name, t.is_public
+        FROM data.file_tag ft
+        JOIN  data.tags t           ON t.id = ft.tag_id
+        JOIN  core.users u          ON u.id = t.creator_id
+        LEFT JOIN data.categories c ON c.id = t.category_id
+        WHERE ft.file_id IN (%s)
+        ORDER BY ft.file_id, t.name`, strings.Join(placeholders, ","))
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sqlStr, args...)
+	if err != nil {
+		return nil, fmt.Errorf("FileRepo.loadTagsBatch: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[fileTagRow])
+	if err != nil {
+		return nil, fmt.Errorf("FileRepo.loadTagsBatch scan: %w", err)
+	}
+
+	result := make(map[uuid.UUID][]domain.Tag, len(fileIDs))
+	for _, fid := range fileIDs {
+		result[fid] = []domain.Tag{} // guarantee every key has a non-nil slice
+	}
+	for _, row := range collected {
+		result[row.FileID] = append(result[row.FileID], toTagFromFileTag(row))
+	}
+	return result, nil
+}
+
+// RecordView appends a row to activity.file_views. viewed_at defaults to
+// statement_timestamp(), so each call records a distinct view in the history.
+func (r *FileRepo) RecordView(ctx context.Context, fileID uuid.UUID, userID int16) error {
+	const query = `INSERT INTO activity.file_views (file_id, user_id) VALUES ($1, $2)`
+	if _, err := connOrTx(ctx, r.pool).Exec(ctx, query, fileID, userID); err != nil {
+		return fmt.Errorf("FileRepo.RecordView: %w", err)
+	}
+	return nil
+}
+
+// RecordTagUses appends a row to activity.tag_uses for each tag referenced in a
+// filter DSL, flagging it included (positive) or excluded (negated). Tags are
+// deduplicated per call, so one statement_timestamp() never collides on the
+// (tag_id, used_at, user_id) PK; ON CONFLICT DO NOTHING guards the rest. A
+// filter with no tag terms is a no-op.
+func (r *FileRepo) RecordTagUses(ctx context.Context, userID int16, filterDSL string) error {
+	uses := filterTagUses(filterDSL)
+	if len(uses) == 0 {
+		return nil
+	}
+
+	var sb strings.Builder
+	sb.WriteString("INSERT INTO activity.tag_uses (tag_id, user_id, is_included) VALUES ")
+	args := make([]any, 0, len(uses)*3)
+	for i, u := range uses {
+		if i > 0 {
+			sb.WriteString(", ")
+		}
+		base := i * 3
+		fmt.Fprintf(&sb, "($%d, $%d, $%d)", base+1, base+2, base+3)
+		args = append(args, u.tagID, userID, u.included)
+	}
+	sb.WriteString(" ON CONFLICT DO NOTHING")
+
+	if _, err := connOrTx(ctx, r.pool).Exec(ctx, sb.String(), args...); err != nil {
+		return fmt.Errorf("FileRepo.RecordTagUses: %w", err)
+	}
+	return nil
+}

backend/internal/db/postgres/filter_parser.go

@@ -0,0 +1,348 @@
+package postgres
+
+import (
+	"fmt"
+	"strconv"
+	"strings"
+
+	"github.com/google/uuid"
+)
+
+// ---------------------------------------------------------------------------
+// Token types
+// ---------------------------------------------------------------------------
+
+type filterTokenKind int
+
+const (
+	ftkAnd filterTokenKind = iota
+	ftkOr
+	ftkNot
+	ftkLParen
+	ftkRParen
+	ftkTag       // t=<uuid>
+	ftkMimeExact // m=<int>
+	ftkMimeLike  // m~<pattern>
+)
+
+type filterToken struct {
+	kind     filterTokenKind
+	tagID    uuid.UUID // ftkTag
+	untagged bool      // ftkTag with zero UUID → "file has no tags"
+	mimeID   int16     // ftkMimeExact
+	pattern  string    // ftkMimeLike
+}
+
+// ---------------------------------------------------------------------------
+// AST nodes
+// ---------------------------------------------------------------------------
+
+// filterNode produces a parameterized SQL fragment.
+// n is the index of the next available positional parameter ($n).
+// Returns the fragment, the updated n, and the extended args slice.
+type filterNode interface {
+	toSQL(n int, args []any) (string, int, []any)
+}
+
+type andNode struct{ left, right filterNode }
+type orNode struct{ left, right filterNode }
+type notNode struct{ child filterNode }
+type leafNode struct{ tok filterToken }
+
+func (a *andNode) toSQL(n int, args []any) (string, int, []any) {
+	ls, n, args := a.left.toSQL(n, args)
+	rs, n, args := a.right.toSQL(n, args)
+	return "(" + ls + " AND " + rs + ")", n, args
+}
+
+func (o *orNode) toSQL(n int, args []any) (string, int, []any) {
+	ls, n, args := o.left.toSQL(n, args)
+	rs, n, args := o.right.toSQL(n, args)
+	return "(" + ls + " OR " + rs + ")", n, args
+}
+
+func (no *notNode) toSQL(n int, args []any) (string, int, []any) {
+	cs, n, args := no.child.toSQL(n, args)
+	return "(NOT " + cs + ")", n, args
+}
+
+func (l *leafNode) toSQL(n int, args []any) (string, int, []any) {
+	switch l.tok.kind {
+	case ftkTag:
+		if l.tok.untagged {
+			return "NOT EXISTS (SELECT 1 FROM data.file_tag ft WHERE ft.file_id = f.id)", n, args
+		}
+		s := fmt.Sprintf(
+			"EXISTS (SELECT 1 FROM data.file_tag ft WHERE ft.file_id = f.id AND ft.tag_id = $%d)", n)
+		return s, n + 1, append(args, l.tok.tagID)
+	case ftkMimeExact:
+		return fmt.Sprintf("f.mime_id = $%d", n), n + 1, append(args, l.tok.mimeID)
+	case ftkMimeLike:
+		// mt alias comes from the JOIN in the main file query (always present).
+		return fmt.Sprintf("mt.name LIKE $%d", n), n + 1, append(args, l.tok.pattern)
+	}
+	panic("filterNode.toSQL: unknown leaf kind")
+}
+
+// ---------------------------------------------------------------------------
+// Lexer
+// ---------------------------------------------------------------------------
+
+// lexFilter tokenises the DSL string {a,b,c,...} into filterTokens.
+func lexFilter(dsl string) ([]filterToken, error) {
+	dsl = strings.TrimSpace(dsl)
+	if !strings.HasPrefix(dsl, "{") || !strings.HasSuffix(dsl, "}") {
+		return nil, fmt.Errorf("filter DSL must be wrapped in braces: {…}")
+	}
+	inner := strings.TrimSpace(dsl[1 : len(dsl)-1])
+	if inner == "" {
+		return nil, nil
+	}
+
+	parts := strings.Split(inner, ",")
+	tokens := make([]filterToken, 0, len(parts))
+
+	for _, raw := range parts {
+		p := strings.TrimSpace(raw)
+		switch {
+		case p == "&":
+			tokens = append(tokens, filterToken{kind: ftkAnd})
+		case p == "|":
+			tokens = append(tokens, filterToken{kind: ftkOr})
+		case p == "!":
+			tokens = append(tokens, filterToken{kind: ftkNot})
+		case p == "(":
+			tokens = append(tokens, filterToken{kind: ftkLParen})
+		case p == ")":
+			tokens = append(tokens, filterToken{kind: ftkRParen})
+		case strings.HasPrefix(p, "t="):
+			id, err := uuid.Parse(p[2:])
+			if err != nil {
+				return nil, fmt.Errorf("filter: invalid tag UUID %q", p[2:])
+			}
+			tokens = append(tokens, filterToken{kind: ftkTag, tagID: id, untagged: id == uuid.Nil})
+		case strings.HasPrefix(p, "m="):
+			v, err := strconv.ParseInt(p[2:], 10, 16)
+			if err != nil {
+				return nil, fmt.Errorf("filter: invalid MIME ID %q", p[2:])
+			}
+			tokens = append(tokens, filterToken{kind: ftkMimeExact, mimeID: int16(v)})
+		case strings.HasPrefix(p, "m~"):
+			// The pattern value is passed as a query parameter, so no SQL injection risk.
+			tokens = append(tokens, filterToken{kind: ftkMimeLike, pattern: p[2:]})
+		default:
+			return nil, fmt.Errorf("filter: unknown token %q", p)
+		}
+	}
+	return tokens, nil
+}
+
+// ---------------------------------------------------------------------------
+// Recursive-descent parser
+// ---------------------------------------------------------------------------
+
+type filterParser struct {
+	tokens []filterToken
+	pos    int
+}
+
+func (p *filterParser) peek() (filterToken, bool) {
+	if p.pos >= len(p.tokens) {
+		return filterToken{}, false
+	}
+	return p.tokens[p.pos], true
+}
+
+func (p *filterParser) next() filterToken {
+	t := p.tokens[p.pos]
+	p.pos++
+	return t
+}
+
+// Grammar (standard NOT > AND > OR precedence):
+//
+//	expr     := or_expr
+//	or_expr  := and_expr ('|' and_expr)*
+//	and_expr := not_expr ('&' not_expr)*
+//	not_expr := '!' not_expr | atom
+//	atom     := '(' expr ')' | leaf
+
+func (p *filterParser) parseExpr() (filterNode, error) { return p.parseOr() }
+
+func (p *filterParser) parseOr() (filterNode, error) {
+	left, err := p.parseAnd()
+	if err != nil {
+		return nil, err
+	}
+	for {
+		t, ok := p.peek()
+		if !ok || t.kind != ftkOr {
+			break
+		}
+		p.next()
+		right, err := p.parseAnd()
+		if err != nil {
+			return nil, err
+		}
+		left = &orNode{left, right}
+	}
+	return left, nil
+}
+
+func (p *filterParser) parseAnd() (filterNode, error) {
+	left, err := p.parseNot()
+	if err != nil {
+		return nil, err
+	}
+	for {
+		t, ok := p.peek()
+		if !ok || t.kind != ftkAnd {
+			break
+		}
+		p.next()
+		right, err := p.parseNot()
+		if err != nil {
+			return nil, err
+		}
+		left = &andNode{left, right}
+	}
+	return left, nil
+}
+
+func (p *filterParser) parseNot() (filterNode, error) {
+	t, ok := p.peek()
+	if ok && t.kind == ftkNot {
+		p.next()
+		child, err := p.parseNot() // right-recursive to allow !!x
+		if err != nil {
+			return nil, err
+		}
+		return &notNode{child}, nil
+	}
+	return p.parseAtom()
+}
+
+func (p *filterParser) parseAtom() (filterNode, error) {
+	t, ok := p.peek()
+	if !ok {
+		return nil, fmt.Errorf("filter: unexpected end of expression")
+	}
+	if t.kind == ftkLParen {
+		p.next()
+		expr, err := p.parseExpr()
+		if err != nil {
+			return nil, err
+		}
+		rp, ok := p.peek()
+		if !ok || rp.kind != ftkRParen {
+			return nil, fmt.Errorf("filter: expected ')'")
+		}
+		p.next()
+		return expr, nil
+	}
+	switch t.kind {
+	case ftkTag, ftkMimeExact, ftkMimeLike:
+		p.next()
+		return &leafNode{t}, nil
+	default:
+		return nil, fmt.Errorf("filter: unexpected token at position %d", p.pos)
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Public entry point
+// ---------------------------------------------------------------------------
+
+// parseFilterAST lexes and parses a filter DSL into an AST. Returns (nil, nil)
+// for an empty or trivial DSL.
+func parseFilterAST(dsl string) (filterNode, error) {
+	dsl = strings.TrimSpace(dsl)
+	if dsl == "" || dsl == "{}" {
+		return nil, nil
+	}
+	toks, err := lexFilter(dsl)
+	if err != nil {
+		return nil, err
+	}
+	if len(toks) == 0 {
+		return nil, nil
+	}
+	p := &filterParser{tokens: toks}
+	node, err := p.parseExpr()
+	if err != nil {
+		return nil, err
+	}
+	if p.pos != len(p.tokens) {
+		return nil, fmt.Errorf("filter: trailing tokens at position %d", p.pos)
+	}
+	return node, nil
+}
+
+// ParseFilter parses a filter DSL string into a parameterized SQL fragment.
+//
+// argStart is the 1-based index for the first $N placeholder; this lets the
+// caller interleave filter parameters with other query parameters.
+//
+// Returns ("", argStart, nil, nil) for an empty or trivial DSL.
+// SQL injection is structurally impossible: every user-supplied value is
+// bound as a query parameter ($N), never interpolated into the SQL string.
+func ParseFilter(dsl string, argStart int) (sql string, nextN int, args []any, err error) {
+	node, err := parseFilterAST(dsl)
+	if err != nil {
+		return "", argStart, nil, err
+	}
+	if node == nil {
+		return "", argStart, nil, nil
+	}
+	sql, nextN, args = node.toSQL(argStart, nil)
+	return sql, nextN, args, nil
+}
+
+// tagUse is a tag referenced by a filter, with whether it was included
+// (positive) or excluded (negated under an odd number of NOTs).
+type tagUse struct {
+	tagID    uuid.UUID
+	included bool
+}
+
+// filterTagUses extracts the distinct tag references in a filter DSL, marking
+// each as included or excluded. The "untagged" pseudo-token (zero UUID) is
+// skipped. Returns nil for a filter with no tag terms; an unparseable filter
+// also yields nil (extraction is best-effort analytics, not validation).
+func filterTagUses(dsl string) []tagUse {
+	node, err := parseFilterAST(dsl)
+	if err != nil || node == nil {
+		return nil
+	}
+	seen := make(map[uuid.UUID]bool)
+	collectTagUses(node, true, seen)
+	if len(seen) == 0 {
+		return nil
+	}
+	uses := make([]tagUse, 0, len(seen))
+	for id, inc := range seen {
+		uses = append(uses, tagUse{tagID: id, included: inc})
+	}
+	return uses
+}
+
+// collectTagUses walks the AST, recording each real tag leaf into out keyed by
+// id. included flips under every NOT, so a tag is "excluded" only when nested
+// under an odd number of NOTs. A tag appearing under both polarities keeps the
+// last seen — pathological, but it avoids a duplicate-key insert.
+func collectTagUses(node filterNode, included bool, out map[uuid.UUID]bool) {
+	switch nd := node.(type) {
+	case *andNode:
+		collectTagUses(nd.left, included, out)
+		collectTagUses(nd.right, included, out)
+	case *orNode:
+		collectTagUses(nd.left, included, out)
+		collectTagUses(nd.right, included, out)
+	case *notNode:
+		collectTagUses(nd.child, !included, out)
+	case *leafNode:
+		if nd.tok.kind == ftkTag && !nd.tok.untagged {
+			out[nd.tok.tagID] = included
+		}
+	}
+}

backend/internal/db/postgres/filter_parser_test.go

@@ -0,0 +1,53 @@
+package postgres
+
+import (
+	"testing"
+
+	"github.com/google/uuid"
+)
+
+func TestFilterTagUses(t *testing.T) {
+	a := uuid.MustParse("11111111-1111-1111-1111-111111111111")
+	b := uuid.MustParse("22222222-2222-2222-2222-222222222222")
+
+	tests := []struct {
+		name string
+		dsl  string
+		want map[uuid.UUID]bool // tag → included; absence means "not recorded"
+	}{
+		{"single included", "{t=" + a.String() + "}", map[uuid.UUID]bool{a: true}},
+		{"single excluded", "{!,t=" + a.String() + "}", map[uuid.UUID]bool{a: false}},
+		{"double negation is included", "{!,!,t=" + a.String() + "}", map[uuid.UUID]bool{a: true}},
+		{
+			"and of two included",
+			"{t=" + a.String() + ",&,t=" + b.String() + "}",
+			map[uuid.UUID]bool{a: true, b: true},
+		},
+		{
+			"not over a group excludes both",
+			"{!,(,t=" + a.String() + ",|,t=" + b.String() + ",)}",
+			map[uuid.UUID]bool{a: false, b: false},
+		},
+		{"untagged pseudo-token skipped", "{t=" + uuid.Nil.String() + "}", map[uuid.UUID]bool{}},
+		{"mime-only filter records nothing", "{m=3}", map[uuid.UUID]bool{}},
+		{"empty filter", "{}", map[uuid.UUID]bool{}},
+		{"unparseable filter is best-effort nil", "{t=not-a-uuid}", map[uuid.UUID]bool{}},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			got := make(map[uuid.UUID]bool)
+			for _, u := range filterTagUses(tc.dsl) {
+				got[u.tagID] = u.included
+			}
+			if len(got) != len(tc.want) {
+				t.Fatalf("got %d uses %v, want %d %v", len(got), got, len(tc.want), tc.want)
+			}
+			for id, inc := range tc.want {
+				if g, ok := got[id]; !ok || g != inc {
+					t.Errorf("tag %s: got (included=%v, present=%v), want included=%v", id, g, ok, inc)
+				}
+			}
+		})
+	}
+}

backend/internal/db/postgres/mime_repo.go

@@ -0,0 +1,97 @@
+package postgres
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+type mimeRow struct {
+	ID        int16  `db:"id"`
+	Name      string `db:"name"`
+	Extension string `db:"extension"`
+}
+
+func toMIMEType(r mimeRow) domain.MIMEType {
+	return domain.MIMEType{
+		ID:        r.ID,
+		Name:      r.Name,
+		Extension: r.Extension,
+	}
+}
+
+// MimeRepo implements port.MimeRepo using PostgreSQL.
+type MimeRepo struct {
+	pool *pgxpool.Pool
+}
+
+// NewMimeRepo creates a MimeRepo backed by pool.
+func NewMimeRepo(pool *pgxpool.Pool) *MimeRepo {
+	return &MimeRepo{pool: pool}
+}
+
+var _ port.MimeRepo = (*MimeRepo)(nil)
+
+func (r *MimeRepo) List(ctx context.Context) ([]domain.MIMEType, error) {
+	const sql = `SELECT id, name, extension FROM core.mime_types ORDER BY name`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql)
+	if err != nil {
+		return nil, fmt.Errorf("MimeRepo.List: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[mimeRow])
+	if err != nil {
+		return nil, fmt.Errorf("MimeRepo.List scan: %w", err)
+	}
+
+	result := make([]domain.MIMEType, len(collected))
+	for i, row := range collected {
+		result[i] = toMIMEType(row)
+	}
+	return result, nil
+}
+
+func (r *MimeRepo) GetByID(ctx context.Context, id int16) (*domain.MIMEType, error) {
+	const sql = `SELECT id, name, extension FROM core.mime_types WHERE id = $1`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql, id)
+	if err != nil {
+		return nil, fmt.Errorf("MimeRepo.GetByID: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[mimeRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("MimeRepo.GetByID scan: %w", err)
+	}
+	m := toMIMEType(row)
+	return &m, nil
+}
+
+func (r *MimeRepo) GetByName(ctx context.Context, name string) (*domain.MIMEType, error) {
+	const sql = `SELECT id, name, extension FROM core.mime_types WHERE name = $1`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql, name)
+	if err != nil {
+		return nil, fmt.Errorf("MimeRepo.GetByName: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[mimeRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrUnsupportedMIME
+		}
+		return nil, fmt.Errorf("MimeRepo.GetByName scan: %w", err)
+	}
+	m := toMIMEType(row)
+	return &m, nil
+}

backend/internal/db/postgres/pool_repo.go

@@ -0,0 +1,725 @@
+package postgres
+
+import (
+	"context"
+	"encoding/base64"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+	"time"
+
+	"github.com/google/uuid"
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"tanabata/backend/internal/db"
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+// ---------------------------------------------------------------------------
+// Row structs
+// ---------------------------------------------------------------------------
+
+type poolRow struct {
+	ID          uuid.UUID `db:"id"`
+	Name        string    `db:"name"`
+	Notes       *string   `db:"notes"`
+	Metadata    []byte    `db:"metadata"`
+	CreatorID   int16     `db:"creator_id"`
+	CreatorName string    `db:"creator_name"`
+	IsPublic    bool      `db:"is_public"`
+	FileCount   int       `db:"file_count"`
+}
+
+type poolRowWithTotal struct {
+	poolRow
+	Total int `db:"total"`
+}
+
+// poolFileRow is a flat struct combining all file columns plus pool position.
+type poolFileRow struct {
+	ID              uuid.UUID       `db:"id"`
+	OriginalName    *string         `db:"original_name"`
+	MIMEType        string          `db:"mime_type"`
+	MIMEExtension   string          `db:"mime_extension"`
+	ContentDatetime time.Time       `db:"content_datetime"`
+	Notes           *string         `db:"notes"`
+	Metadata        json.RawMessage `db:"metadata"`
+	EXIF            json.RawMessage `db:"exif"`
+	PHash           *int64          `db:"phash"`
+	CreatorID       int16           `db:"creator_id"`
+	CreatorName     string          `db:"creator_name"`
+	IsPublic        bool            `db:"is_public"`
+	IsDeleted       bool            `db:"is_deleted"`
+	Position        int             `db:"position"`
+}
+
+// ---------------------------------------------------------------------------
+// Converters
+// ---------------------------------------------------------------------------
+
+func toPool(r poolRow) domain.Pool {
+	p := domain.Pool{
+		ID:          r.ID,
+		Name:        r.Name,
+		Notes:       r.Notes,
+		CreatorID:   r.CreatorID,
+		CreatorName: r.CreatorName,
+		IsPublic:    r.IsPublic,
+		FileCount:   r.FileCount,
+		CreatedAt:   domain.UUIDCreatedAt(r.ID),
+	}
+	if len(r.Metadata) > 0 && string(r.Metadata) != "null" {
+		p.Metadata = json.RawMessage(r.Metadata)
+	}
+	return p
+}
+
+func toPoolFile(r poolFileRow) domain.PoolFile {
+	return domain.PoolFile{
+		File: domain.File{
+			ID:              r.ID,
+			OriginalName:    r.OriginalName,
+			MIMEType:        r.MIMEType,
+			MIMEExtension:   r.MIMEExtension,
+			ContentDatetime: r.ContentDatetime,
+			Notes:           r.Notes,
+			Metadata:        r.Metadata,
+			EXIF:            r.EXIF,
+			PHash:           r.PHash,
+			CreatorID:       r.CreatorID,
+			CreatorName:     r.CreatorName,
+			IsPublic:        r.IsPublic,
+			IsDeleted:       r.IsDeleted,
+			CreatedAt:       domain.UUIDCreatedAt(r.ID),
+		},
+		Position: r.Position,
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Cursor
+// ---------------------------------------------------------------------------
+
+type poolFileCursor struct {
+	Position int    `json:"p"`
+	FileID   string `json:"id"`
+}
+
+func encodePoolCursor(c poolFileCursor) string {
+	b, _ := json.Marshal(c)
+	return base64.RawURLEncoding.EncodeToString(b)
+}
+
+func decodePoolCursor(s string) (poolFileCursor, error) {
+	b, err := base64.RawURLEncoding.DecodeString(s)
+	if err != nil {
+		return poolFileCursor{}, fmt.Errorf("cursor: invalid encoding")
+	}
+	var c poolFileCursor
+	if err := json.Unmarshal(b, &c); err != nil {
+		return poolFileCursor{}, fmt.Errorf("cursor: invalid format")
+	}
+	return c, nil
+}
+
+// ---------------------------------------------------------------------------
+// Shared SQL
+// ---------------------------------------------------------------------------
+
+// poolCountSubquery computes per-pool file counts.
+const poolCountSubquery = `(SELECT pool_id, COUNT(*) AS cnt FROM data.file_pool GROUP BY pool_id)`
+
+const poolSelectFrom = `
+SELECT p.id, p.name, p.notes, p.metadata,
+       p.creator_id, u.name AS creator_name, p.is_public,
+       COALESCE(fc.cnt, 0) AS file_count
+FROM data.pools p
+JOIN core.users u ON u.id = p.creator_id
+LEFT JOIN ` + poolCountSubquery + ` fc ON fc.pool_id = p.id`
+
+func poolSortColumn(s string) string {
+	if s == "name" {
+		return "p.name"
+	}
+	return "p.id" // "created"
+}
+
+// ---------------------------------------------------------------------------
+// PoolRepo
+// ---------------------------------------------------------------------------
+
+// PoolRepo implements port.PoolRepo using PostgreSQL.
+type PoolRepo struct {
+	pool *pgxpool.Pool
+}
+
+var _ port.PoolRepo = (*PoolRepo)(nil)
+
+// NewPoolRepo creates a PoolRepo backed by pool.
+func NewPoolRepo(pool *pgxpool.Pool) *PoolRepo {
+	return &PoolRepo{pool: pool}
+}
+
+// ---------------------------------------------------------------------------
+// List
+// ---------------------------------------------------------------------------
+
+func (r *PoolRepo) List(ctx context.Context, params port.OffsetParams) (*domain.PoolOffsetPage, error) {
+	order := "ASC"
+	if strings.ToLower(params.Order) == "desc" {
+		order = "DESC"
+	}
+	sortCol := poolSortColumn(params.Sort)
+
+	args := []any{}
+	n := 1
+	var conditions []string
+
+	if params.Search != "" {
+		conditions = append(conditions, fmt.Sprintf("lower(p.name) LIKE lower($%d)", n))
+		args = append(args, "%"+params.Search+"%")
+		n++
+	}
+	// Restrict to pools the viewer may see (private-by-default), unless admin.
+	if !params.ViewerIsAdmin {
+		var aclCond string
+		aclCond, n, args = aclVisibilityCond("p", objTypePool, params.ViewerID, n, args)
+		conditions = append(conditions, aclCond)
+	}
+
+	where := ""
+	if len(conditions) > 0 {
+		where = "WHERE " + strings.Join(conditions, " AND ")
+	}
+
+	limit := params.Limit
+	if limit <= 0 {
+		limit = 50
+	}
+	offset := params.Offset
+	if offset < 0 {
+		offset = 0
+	}
+
+	query := fmt.Sprintf(`
+SELECT p.id, p.name, p.notes, p.metadata,
+       p.creator_id, u.name AS creator_name, p.is_public,
+       COALESCE(fc.cnt, 0) AS file_count,
+       COUNT(*) OVER() AS total
+FROM data.pools p
+JOIN core.users u ON u.id = p.creator_id
+LEFT JOIN %s fc ON fc.pool_id = p.id
+%s
+ORDER BY %s %s NULLS LAST, p.id ASC
+LIMIT $%d OFFSET $%d`, poolCountSubquery, where, sortCol, order, n, n+1)
+
+	args = append(args, limit, offset)
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query, args...)
+	if err != nil {
+		return nil, fmt.Errorf("PoolRepo.List query: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[poolRowWithTotal])
+	if err != nil {
+		return nil, fmt.Errorf("PoolRepo.List scan: %w", err)
+	}
+
+	items := make([]domain.Pool, len(collected))
+	total := 0
+	for i, row := range collected {
+		items[i] = toPool(row.poolRow)
+		total = row.Total
+	}
+	return &domain.PoolOffsetPage{
+		Items:  items,
+		Total:  total,
+		Offset: offset,
+		Limit:  limit,
+	}, nil
+}
+
+// ---------------------------------------------------------------------------
+// GetByID
+// ---------------------------------------------------------------------------
+
+func (r *PoolRepo) GetByID(ctx context.Context, id uuid.UUID) (*domain.Pool, error) {
+	query := poolSelectFrom + `
+WHERE p.id = $1`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query, id)
+	if err != nil {
+		return nil, fmt.Errorf("PoolRepo.GetByID: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[poolRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("PoolRepo.GetByID scan: %w", err)
+	}
+	p := toPool(row)
+	return &p, nil
+}
+
+// RecordView appends a row to activity.pool_views. viewed_at defaults to
+// statement_timestamp(), so each call records a distinct view in the history.
+func (r *PoolRepo) RecordView(ctx context.Context, poolID uuid.UUID, userID int16) error {
+	const query = `INSERT INTO activity.pool_views (pool_id, user_id) VALUES ($1, $2)`
+	if _, err := connOrTx(ctx, r.pool).Exec(ctx, query, poolID, userID); err != nil {
+		return fmt.Errorf("PoolRepo.RecordView: %w", err)
+	}
+	return nil
+}
+
+// ---------------------------------------------------------------------------
+// Create
+// ---------------------------------------------------------------------------
+
+func (r *PoolRepo) Create(ctx context.Context, p *domain.Pool) (*domain.Pool, error) {
+	const query = `
+WITH ins AS (
+    INSERT INTO data.pools (name, notes, metadata, creator_id, is_public)
+    VALUES ($1, $2, $3, $4, $5)
+    RETURNING *
+)
+SELECT ins.id, ins.name, ins.notes, ins.metadata,
+       ins.creator_id, u.name AS creator_name, ins.is_public,
+       0 AS file_count
+FROM ins
+JOIN core.users u ON u.id = ins.creator_id`
+
+	var meta any
+	if len(p.Metadata) > 0 {
+		meta = p.Metadata
+	}
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query, p.Name, p.Notes, meta, p.CreatorID, p.IsPublic)
+	if err != nil {
+		return nil, fmt.Errorf("PoolRepo.Create: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[poolRow])
+	if err != nil {
+		if isPgUniqueViolation(err) {
+			return nil, domain.ErrConflict
+		}
+		return nil, fmt.Errorf("PoolRepo.Create scan: %w", err)
+	}
+	created := toPool(row)
+	return &created, nil
+}
+
+// ---------------------------------------------------------------------------
+// Update
+// ---------------------------------------------------------------------------
+
+func (r *PoolRepo) Update(ctx context.Context, id uuid.UUID, p *domain.Pool) (*domain.Pool, error) {
+	const query = `
+WITH upd AS (
+    UPDATE data.pools SET
+        name      = $2,
+        notes     = $3,
+        metadata  = COALESCE($4, metadata),
+        is_public = $5
+    WHERE id = $1
+    RETURNING *
+)
+SELECT upd.id, upd.name, upd.notes, upd.metadata,
+       upd.creator_id, u.name AS creator_name, upd.is_public,
+       COALESCE(fc.cnt, 0) AS file_count
+FROM upd
+JOIN core.users u ON u.id = upd.creator_id
+LEFT JOIN (SELECT pool_id, COUNT(*) AS cnt FROM data.file_pool WHERE pool_id = $1 GROUP BY pool_id) fc
+    ON fc.pool_id = upd.id`
+
+	var meta any
+	if len(p.Metadata) > 0 {
+		meta = p.Metadata
+	}
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query, id, p.Name, p.Notes, meta, p.IsPublic)
+	if err != nil {
+		return nil, fmt.Errorf("PoolRepo.Update: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[poolRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		if isPgUniqueViolation(err) {
+			return nil, domain.ErrConflict
+		}
+		return nil, fmt.Errorf("PoolRepo.Update scan: %w", err)
+	}
+	updated := toPool(row)
+	return &updated, nil
+}
+
+// ---------------------------------------------------------------------------
+// Delete
+// ---------------------------------------------------------------------------
+
+func (r *PoolRepo) Delete(ctx context.Context, id uuid.UUID) error {
+	const query = `DELETE FROM data.pools WHERE id = $1`
+	q := connOrTx(ctx, r.pool)
+	ct, err := q.Exec(ctx, query, id)
+	if err != nil {
+		return fmt.Errorf("PoolRepo.Delete: %w", err)
+	}
+	if ct.RowsAffected() == 0 {
+		return domain.ErrNotFound
+	}
+	return nil
+}
+
+// ---------------------------------------------------------------------------
+// ListFiles
+// ---------------------------------------------------------------------------
+
+// fileSelectForPool is the column list for pool file queries (without position).
+const fileSelectForPool = `
+    f.id, f.original_name,
+    mt.name AS mime_type, mt.extension AS mime_extension,
+    f.content_datetime, f.notes, f.metadata, f.exif, f.phash,
+    f.creator_id, u.name AS creator_name,
+    f.is_public, f.is_deleted`
+
+func (r *PoolRepo) ListFiles(ctx context.Context, poolID uuid.UUID, params port.PoolFileListParams) (*domain.PoolFilePage, error) {
+	limit := db.ClampLimit(params.Limit, 50, 200)
+
+	args := []any{poolID}
+	n := 2
+	var conds []string
+
+	conds = append(conds, "fp.pool_id = $1")
+	conds = append(conds, "f.is_deleted = false")
+
+	if params.Filter != "" {
+		filterSQL, nextN, filterArgs, err := ParseFilter(params.Filter, n)
+		if err != nil {
+			return nil, fmt.Errorf("%w: %v", domain.ErrValidation, err)
+		}
+		if filterSQL != "" {
+			conds = append(conds, filterSQL)
+			n = nextN
+			args = append(args, filterArgs...)
+		}
+	}
+
+	// Cursor condition.
+	var orderBy string
+	if params.Cursor != "" {
+		cur, err := decodePoolCursor(params.Cursor)
+		if err != nil {
+			return nil, fmt.Errorf("%w: %v", domain.ErrValidation, err)
+		}
+		fileID, err := uuid.Parse(cur.FileID)
+		if err != nil {
+			return nil, domain.ErrValidation
+		}
+		conds = append(conds, fmt.Sprintf(
+			"(fp.position > $%d OR (fp.position = $%d AND fp.file_id > $%d))",
+			n, n, n+1))
+		args = append(args, cur.Position, fileID)
+		n += 2
+	}
+	orderBy = "fp.position ASC, fp.file_id ASC"
+
+	where := "WHERE " + strings.Join(conds, " AND ")
+	args = append(args, limit+1)
+
+	sqlStr := fmt.Sprintf(`
+SELECT %s, fp.position
+FROM data.file_pool fp
+JOIN data.files f       ON f.id  = fp.file_id
+JOIN core.mime_types mt ON mt.id = f.mime_id
+JOIN core.users u       ON u.id  = f.creator_id
+%s
+ORDER BY %s
+LIMIT $%d`, fileSelectForPool, where, orderBy, n)
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sqlStr, args...)
+	if err != nil {
+		return nil, fmt.Errorf("PoolRepo.ListFiles query: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[poolFileRow])
+	if err != nil {
+		return nil, fmt.Errorf("PoolRepo.ListFiles scan: %w", err)
+	}
+
+	hasMore := len(collected) > limit
+	if hasMore {
+		collected = collected[:limit]
+	}
+
+	items := make([]domain.PoolFile, len(collected))
+	for i, row := range collected {
+		items[i] = toPoolFile(row)
+	}
+
+	page := &domain.PoolFilePage{Items: items}
+
+	if hasMore && len(collected) > 0 {
+		last := collected[len(collected)-1]
+		cur := encodePoolCursor(poolFileCursor{
+			Position: last.Position,
+			FileID:   last.ID.String(),
+		})
+		page.NextCursor = &cur
+	}
+
+	// Batch-load tags.
+	if len(items) > 0 {
+		fileIDs := make([]uuid.UUID, len(items))
+		for i, pf := range items {
+			fileIDs[i] = pf.File.ID
+		}
+		tagMap, err := r.loadPoolTagsBatch(ctx, fileIDs)
+		if err != nil {
+			return nil, err
+		}
+		for i, pf := range items {
+			page.Items[i].File.Tags = tagMap[pf.File.ID]
+		}
+	}
+
+	return page, nil
+}
+
+// loadPoolTagsBatch re-uses the same pattern as FileRepo.loadTagsBatch.
+func (r *PoolRepo) loadPoolTagsBatch(ctx context.Context, fileIDs []uuid.UUID) (map[uuid.UUID][]domain.Tag, error) {
+	if len(fileIDs) == 0 {
+		return nil, nil
+	}
+	placeholders := make([]string, len(fileIDs))
+	args := make([]any, len(fileIDs))
+	for i, id := range fileIDs {
+		placeholders[i] = fmt.Sprintf("$%d", i+1)
+		args[i] = id
+	}
+	sqlStr := fmt.Sprintf(`
+SELECT ft.file_id,
+       t.id, t.name, t.notes, t.color,
+       t.category_id,
+       c.name  AS category_name,
+       c.color AS category_color,
+       t.metadata, t.creator_id, u.name AS creator_name, t.is_public
+FROM data.file_tag ft
+JOIN  data.tags t           ON t.id = ft.tag_id
+JOIN  core.users u          ON u.id = t.creator_id
+LEFT JOIN data.categories c ON c.id = t.category_id
+WHERE ft.file_id IN (%s)
+ORDER BY ft.file_id, t.name`, strings.Join(placeholders, ","))
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sqlStr, args...)
+	if err != nil {
+		return nil, fmt.Errorf("PoolRepo.loadPoolTagsBatch: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[fileTagRow])
+	if err != nil {
+		return nil, fmt.Errorf("PoolRepo.loadPoolTagsBatch scan: %w", err)
+	}
+	result := make(map[uuid.UUID][]domain.Tag, len(fileIDs))
+	for _, fid := range fileIDs {
+		result[fid] = []domain.Tag{}
+	}
+	for _, row := range collected {
+		result[row.FileID] = append(result[row.FileID], toTagFromFileTag(row))
+	}
+	return result, nil
+}
+
+// ---------------------------------------------------------------------------
+// AddFiles
+// ---------------------------------------------------------------------------
+
+// AddFiles inserts files into the pool. When position is nil, files are
+// appended after the last existing file (MAX(position) + 1000 * i).
+// When position is provided (0-indexed), files are inserted at that index
+// and all pool positions are reassigned in one shot.
+func (r *PoolRepo) AddFiles(ctx context.Context, poolID uuid.UUID, fileIDs []uuid.UUID, position *int) error {
+	if len(fileIDs) == 0 {
+		return nil
+	}
+	q := connOrTx(ctx, r.pool)
+
+	if position == nil {
+		// Append: get current max position, then bulk-insert.
+		var maxPos int
+		row := q.QueryRow(ctx, `SELECT COALESCE(MAX(position), 0) FROM data.file_pool WHERE pool_id = $1`, poolID)
+		if err := row.Scan(&maxPos); err != nil {
+			return fmt.Errorf("PoolRepo.AddFiles maxPos: %w", err)
+		}
+		const ins = `INSERT INTO data.file_pool (file_id, pool_id, position) VALUES ($1, $2, $3) ON CONFLICT DO NOTHING`
+		for i, fid := range fileIDs {
+			if _, err := q.Exec(ctx, ins, fid, poolID, maxPos+1000*(i+1)); err != nil {
+				return fmt.Errorf("PoolRepo.AddFiles insert: %w", err)
+			}
+		}
+		return nil
+	}
+
+	// Positional insert: rebuild the full ordered list and reassign.
+	return r.insertAtPosition(ctx, q, poolID, fileIDs, *position)
+}
+
+// insertAtPosition fetches the current ordered file list, splices in the new
+// IDs at index pos (0-indexed, clamped), then does a full position reassign.
+func (r *PoolRepo) insertAtPosition(ctx context.Context, q db.Querier, poolID uuid.UUID, newIDs []uuid.UUID, pos int) error {
+	// 1. Fetch current order.
+	rows, err := q.Query(ctx, `SELECT file_id FROM data.file_pool WHERE pool_id = $1 ORDER BY position ASC, file_id ASC`, poolID)
+	if err != nil {
+		return fmt.Errorf("PoolRepo.insertAtPosition fetch: %w", err)
+	}
+	var current []uuid.UUID
+	for rows.Next() {
+		var fid uuid.UUID
+		if err := rows.Scan(&fid); err != nil {
+			rows.Close()
+			return fmt.Errorf("PoolRepo.insertAtPosition scan: %w", err)
+		}
+		current = append(current, fid)
+	}
+	rows.Close()
+	if err := rows.Err(); err != nil {
+		return fmt.Errorf("PoolRepo.insertAtPosition rows: %w", err)
+	}
+
+	// 2. Build new ordered list, skipping already-present IDs from newIDs.
+	present := make(map[uuid.UUID]bool, len(current))
+	for _, fid := range current {
+		present[fid] = true
+	}
+	toAdd := make([]uuid.UUID, 0, len(newIDs))
+	for _, fid := range newIDs {
+		if !present[fid] {
+			toAdd = append(toAdd, fid)
+		}
+	}
+	if len(toAdd) == 0 {
+		return nil // all already present
+	}
+
+	if pos < 0 {
+		pos = 0
+	}
+	if pos > len(current) {
+		pos = len(current)
+	}
+
+	ordered := make([]uuid.UUID, 0, len(current)+len(toAdd))
+	ordered = append(ordered, current[:pos]...)
+	ordered = append(ordered, toAdd...)
+	ordered = append(ordered, current[pos:]...)
+
+	// 3. Full replace.
+	return r.reassignPositions(ctx, q, poolID, ordered)
+}
+
+// reassignPositions does a DELETE + bulk INSERT for the pool with positions
+// 1000, 2000, 3000, ...
+func (r *PoolRepo) reassignPositions(ctx context.Context, q db.Querier, poolID uuid.UUID, ordered []uuid.UUID) error {
+	if _, err := q.Exec(ctx, `DELETE FROM data.file_pool WHERE pool_id = $1`, poolID); err != nil {
+		return fmt.Errorf("PoolRepo.reassignPositions delete: %w", err)
+	}
+	if len(ordered) == 0 {
+		return nil
+	}
+	const ins = `INSERT INTO data.file_pool (file_id, pool_id, position) VALUES ($1, $2, $3)`
+	for i, fid := range ordered {
+		if _, err := q.Exec(ctx, ins, fid, poolID, 1000*(i+1)); err != nil {
+			return fmt.Errorf("PoolRepo.reassignPositions insert: %w", err)
+		}
+	}
+	return nil
+}
+
+// ---------------------------------------------------------------------------
+// RemoveFiles
+// ---------------------------------------------------------------------------
+
+func (r *PoolRepo) RemoveFiles(ctx context.Context, poolID uuid.UUID, fileIDs []uuid.UUID) error {
+	if len(fileIDs) == 0 {
+		return nil
+	}
+	placeholders := make([]string, len(fileIDs))
+	args := make([]any, len(fileIDs)+1)
+	args[0] = poolID
+	for i, fid := range fileIDs {
+		placeholders[i] = fmt.Sprintf("$%d", i+2)
+		args[i+1] = fid
+	}
+	query := fmt.Sprintf(
+		`DELETE FROM data.file_pool WHERE pool_id = $1 AND file_id IN (%s)`,
+		strings.Join(placeholders, ","))
+
+	q := connOrTx(ctx, r.pool)
+	if _, err := q.Exec(ctx, query, args...); err != nil {
+		return fmt.Errorf("PoolRepo.RemoveFiles: %w", err)
+	}
+	return nil
+}
+
+// ---------------------------------------------------------------------------
+// Reorder
+// ---------------------------------------------------------------------------
+
+// Reorder applies the requested order to the pool. Files actually in the pool
+// are placed in the given order; any pool members the request omitted are kept
+// and appended in their current order. This makes a partial request (e.g. a
+// paginated client that only loaded the first pages) reorder the visible prefix
+// without deleting the rest. Unknown IDs are ignored.
+func (r *PoolRepo) Reorder(ctx context.Context, poolID uuid.UUID, fileIDs []uuid.UUID) error {
+	q := connOrTx(ctx, r.pool)
+
+	// Current membership, in position order.
+	rows, err := q.Query(ctx,
+		`SELECT file_id FROM data.file_pool WHERE pool_id = $1 ORDER BY position ASC, file_id ASC`, poolID)
+	if err != nil {
+		return fmt.Errorf("PoolRepo.Reorder fetch: %w", err)
+	}
+	var current []uuid.UUID
+	for rows.Next() {
+		var fid uuid.UUID
+		if err := rows.Scan(&fid); err != nil {
+			rows.Close()
+			return fmt.Errorf("PoolRepo.Reorder scan: %w", err)
+		}
+		current = append(current, fid)
+	}
+	rows.Close()
+	if err := rows.Err(); err != nil {
+		return fmt.Errorf("PoolRepo.Reorder rows: %w", err)
+	}
+
+	inPool := make(map[uuid.UUID]bool, len(current))
+	for _, fid := range current {
+		inPool[fid] = true
+	}
+
+	ordered := make([]uuid.UUID, 0, len(current))
+	placed := make(map[uuid.UUID]bool, len(current))
+	for _, fid := range fileIDs {
+		if inPool[fid] && !placed[fid] {
+			ordered = append(ordered, fid)
+			placed[fid] = true
+		}
+	}
+	// Preserve any members the request did not mention.
+	for _, fid := range current {
+		if !placed[fid] {
+			ordered = append(ordered, fid)
+			placed[fid] = true
+		}
+	}
+
+	return r.reassignPositions(ctx, q, poolID, ordered)
+}

backend/internal/db/postgres/postgres.go

@@ -0,0 +1,93 @@
+// Package postgres provides the PostgreSQL implementations of the port interfaces.
+package postgres
+
+import (
+	"context"
+	"fmt"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"tanabata/backend/internal/db"
+)
+
+// NewPool creates and validates a *pgxpool.Pool from the given connection URL.
+// The pool is ready to use; the caller is responsible for closing it.
+func NewPool(ctx context.Context, url string) (*pgxpool.Pool, error) {
+	pool, err := pgxpool.New(ctx, url)
+	if err != nil {
+		return nil, fmt.Errorf("pgxpool.New: %w", err)
+	}
+	if err := pool.Ping(ctx); err != nil {
+		pool.Close()
+		return nil, fmt.Errorf("postgres ping: %w", err)
+	}
+	return pool, nil
+}
+
+// Transactor implements port.Transactor using a pgxpool.Pool.
+type Transactor struct {
+	pool *pgxpool.Pool
+}
+
+// NewTransactor creates a Transactor backed by pool.
+func NewTransactor(pool *pgxpool.Pool) *Transactor {
+	return &Transactor{pool: pool}
+}
+
+// WithTx begins a transaction, stores it in ctx, and calls fn. If fn returns
+// an error the transaction is rolled back; otherwise it is committed.
+func (t *Transactor) WithTx(ctx context.Context, fn func(ctx context.Context) error) error {
+	tx, err := t.pool.BeginTx(ctx, pgx.TxOptions{})
+	if err != nil {
+		return fmt.Errorf("begin tx: %w", err)
+	}
+
+	txCtx := db.ContextWithTx(ctx, tx)
+
+	if err := fn(txCtx); err != nil {
+		_ = tx.Rollback(ctx)
+		return err
+	}
+
+	if err := tx.Commit(ctx); err != nil {
+		return fmt.Errorf("commit tx: %w", err)
+	}
+	return nil
+}
+
+// connOrTx returns the pgx.Tx stored in ctx by WithTx, or the pool itself when
+// no transaction is active. The returned value satisfies db.Querier and can be
+// used directly for queries and commands.
+func connOrTx(ctx context.Context, pool *pgxpool.Pool) db.Querier {
+	if tx, ok := db.TxFromContext(ctx); ok {
+		return tx
+	}
+	return pool
+}
+
+// Object type IDs as seeded in core.object_types (007_seed_data.sql).
+const (
+	objTypeFile     int16 = 1
+	objTypeTag      int16 = 2
+	objTypeCategory int16 = 3
+	objTypePool     int16 = 4
+)
+
+// aclVisibilityCond returns a SQL boolean fragment that is true when the viewer
+// may see the row at <alias>.id of the given object type under the
+// private-by-default model: the row is public, the viewer created it, or the
+// viewer holds an explicit can_view grant. objectTypeID is a trusted constant
+// and is inlined; viewerID is bound as $n (referenced twice). Returns the
+// fragment, the next free parameter index, and the extended args.
+//
+// Callers skip this entirely for admins (who bypass ACL).
+func aclVisibilityCond(alias string, objectTypeID int16, viewerID int16, n int, args []any) (string, int, []any) {
+	cond := fmt.Sprintf(
+		"(%[1]s.is_public OR %[1]s.creator_id = $%[2]d OR EXISTS ("+
+			"SELECT 1 FROM acl.permissions p "+
+			"WHERE p.object_type_id = %[3]d AND p.object_id = %[1]s.id "+
+			"AND p.user_id = $%[2]d AND p.can_view))",
+		alias, n, objectTypeID)
+	return cond, n + 1, append(args, viewerID)
+}

backend/internal/db/postgres/session_repo.go

@@ -0,0 +1,184 @@
+package postgres
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+// sessionRow matches the columns stored in activity.sessions.
+// IsCurrent is a service-layer concern and is not stored in the database.
+type sessionRow struct {
+	ID           int        `db:"id"`
+	TokenHash    string     `db:"token_hash"`
+	UserID       int16      `db:"user_id"`
+	UserAgent    string     `db:"user_agent"`
+	StartedAt    time.Time  `db:"started_at"`
+	ExpiresAt    *time.Time `db:"expires_at"`
+	LastActivity time.Time  `db:"last_activity"`
+}
+
+// sessionRowWithTotal extends sessionRow with a window-function count for ListByUser.
+type sessionRowWithTotal struct {
+	sessionRow
+	Total int `db:"total"`
+}
+
+func toSession(r sessionRow) domain.Session {
+	return domain.Session{
+		ID:           r.ID,
+		TokenHash:    r.TokenHash,
+		UserID:       r.UserID,
+		UserAgent:    r.UserAgent,
+		StartedAt:    r.StartedAt,
+		ExpiresAt:    r.ExpiresAt,
+		LastActivity: r.LastActivity,
+	}
+}
+
+// SessionRepo implements port.SessionRepo using PostgreSQL.
+type SessionRepo struct {
+	pool *pgxpool.Pool
+}
+
+// NewSessionRepo creates a SessionRepo backed by pool.
+func NewSessionRepo(pool *pgxpool.Pool) *SessionRepo {
+	return &SessionRepo{pool: pool}
+}
+
+var _ port.SessionRepo = (*SessionRepo)(nil)
+
+func (r *SessionRepo) Create(ctx context.Context, s *domain.Session) (*domain.Session, error) {
+	const sql = `
+		INSERT INTO activity.sessions (token_hash, user_id, user_agent, expires_at)
+		VALUES ($1, $2, $3, $4)
+		RETURNING id, token_hash, user_id, user_agent, started_at, expires_at, last_activity`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql, s.TokenHash, s.UserID, s.UserAgent, s.ExpiresAt)
+	if err != nil {
+		return nil, fmt.Errorf("SessionRepo.Create: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[sessionRow])
+	if err != nil {
+		return nil, fmt.Errorf("SessionRepo.Create scan: %w", err)
+	}
+	created := toSession(row)
+	return &created, nil
+}
+
+func (r *SessionRepo) GetByID(ctx context.Context, id int) (*domain.Session, error) {
+	const sql = `
+		SELECT id, token_hash, user_id, user_agent, started_at, expires_at, last_activity
+		FROM activity.sessions
+		WHERE id = $1 AND is_active = true`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql, id)
+	if err != nil {
+		return nil, fmt.Errorf("SessionRepo.GetByID: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[sessionRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("SessionRepo.GetByID scan: %w", err)
+	}
+	s := toSession(row)
+	return &s, nil
+}
+
+func (r *SessionRepo) GetByTokenHash(ctx context.Context, hash string) (*domain.Session, error) {
+	const sql = `
+		SELECT id, token_hash, user_id, user_agent, started_at, expires_at, last_activity
+		FROM activity.sessions
+		WHERE token_hash = $1 AND is_active = true`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql, hash)
+	if err != nil {
+		return nil, fmt.Errorf("SessionRepo.GetByTokenHash: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[sessionRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("SessionRepo.GetByTokenHash scan: %w", err)
+	}
+	s := toSession(row)
+	return &s, nil
+}
+
+func (r *SessionRepo) ListByUser(ctx context.Context, userID int16) (*domain.SessionList, error) {
+	const sql = `
+		SELECT id, token_hash, user_id, user_agent, started_at, expires_at, last_activity,
+		       COUNT(*) OVER() AS total
+		FROM activity.sessions
+		WHERE user_id = $1 AND is_active = true
+		ORDER BY started_at DESC`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql, userID)
+	if err != nil {
+		return nil, fmt.Errorf("SessionRepo.ListByUser: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[sessionRowWithTotal])
+	if err != nil {
+		return nil, fmt.Errorf("SessionRepo.ListByUser scan: %w", err)
+	}
+
+	list := &domain.SessionList{}
+	if len(collected) > 0 {
+		list.Total = collected[0].Total
+	}
+	list.Items = make([]domain.Session, len(collected))
+	for i, row := range collected {
+		list.Items[i] = toSession(row.sessionRow)
+	}
+	return list, nil
+}
+
+func (r *SessionRepo) UpdateLastActivity(ctx context.Context, id int, t time.Time) error {
+	const sql = `UPDATE activity.sessions SET last_activity = $2 WHERE id = $1`
+	q := connOrTx(ctx, r.pool)
+	tag, err := q.Exec(ctx, sql, id, t)
+	if err != nil {
+		return fmt.Errorf("SessionRepo.UpdateLastActivity: %w", err)
+	}
+	if tag.RowsAffected() == 0 {
+		return domain.ErrNotFound
+	}
+	return nil
+}
+
+func (r *SessionRepo) Delete(ctx context.Context, id int) error {
+	const sql = `UPDATE activity.sessions SET is_active = false WHERE id = $1 AND is_active = true`
+	q := connOrTx(ctx, r.pool)
+	tag, err := q.Exec(ctx, sql, id)
+	if err != nil {
+		return fmt.Errorf("SessionRepo.Delete: %w", err)
+	}
+	if tag.RowsAffected() == 0 {
+		return domain.ErrNotFound
+	}
+	return nil
+}
+
+func (r *SessionRepo) DeleteByUserID(ctx context.Context, userID int16) error {
+	const sql = `UPDATE activity.sessions SET is_active = false WHERE user_id = $1 AND is_active = true`
+	q := connOrTx(ctx, r.pool)
+	_, err := q.Exec(ctx, sql, userID)
+	if err != nil {
+		return fmt.Errorf("SessionRepo.DeleteByUserID: %w", err)
+	}
+	return nil
+}

backend/internal/db/postgres/tag_repo.go

@@ -0,0 +1,647 @@
+package postgres
+
+import (
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+// ---------------------------------------------------------------------------
+// Row structs — use pgx-scannable types
+// ---------------------------------------------------------------------------
+
+type tagRow struct {
+	ID            uuid.UUID  `db:"id"`
+	Name          string     `db:"name"`
+	Notes         *string    `db:"notes"`
+	Color         *string    `db:"color"`
+	CategoryID    *uuid.UUID `db:"category_id"`
+	CategoryName  *string    `db:"category_name"`
+	CategoryColor *string    `db:"category_color"`
+	Metadata      []byte     `db:"metadata"`
+	CreatorID     int16      `db:"creator_id"`
+	CreatorName   string     `db:"creator_name"`
+	IsPublic      bool       `db:"is_public"`
+}
+
+type tagRowWithTotal struct {
+	tagRow
+	Total int `db:"total"`
+}
+
+type tagRuleRow struct {
+	WhenTagID   uuid.UUID `db:"when_tag_id"`
+	ThenTagID   uuid.UUID `db:"then_tag_id"`
+	ThenTagName string    `db:"then_tag_name"`
+	IsActive    bool      `db:"is_active"`
+}
+
+// ---------------------------------------------------------------------------
+// Converters
+// ---------------------------------------------------------------------------
+
+func toTag(r tagRow) domain.Tag {
+	t := domain.Tag{
+		ID:            r.ID,
+		Name:          r.Name,
+		Notes:         r.Notes,
+		Color:         r.Color,
+		CategoryID:    r.CategoryID,
+		CategoryName:  r.CategoryName,
+		CategoryColor: r.CategoryColor,
+		CreatorID:     r.CreatorID,
+		CreatorName:   r.CreatorName,
+		IsPublic:      r.IsPublic,
+		CreatedAt:     domain.UUIDCreatedAt(r.ID),
+	}
+	if len(r.Metadata) > 0 && string(r.Metadata) != "null" {
+		t.Metadata = json.RawMessage(r.Metadata)
+	}
+	return t
+}
+
+func toTagRule(r tagRuleRow) domain.TagRule {
+	return domain.TagRule{
+		WhenTagID:   r.WhenTagID,
+		ThenTagID:   r.ThenTagID,
+		ThenTagName: r.ThenTagName,
+		IsActive:    r.IsActive,
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Shared SQL fragments
+// ---------------------------------------------------------------------------
+
+const tagSelectFrom = `
+SELECT
+    t.id,
+    t.name,
+    t.notes,
+    t.color,
+    t.category_id,
+    c.name  AS category_name,
+    c.color AS category_color,
+    t.metadata,
+    t.creator_id,
+    u.name  AS creator_name,
+    t.is_public
+FROM data.tags t
+LEFT JOIN data.categories c ON c.id = t.category_id
+JOIN      core.users u ON u.id = t.creator_id`
+
+func tagSortColumn(s string) string {
+	switch s {
+	case "name":
+		return "t.name"
+	case "color":
+		return "t.color"
+	case "category_name":
+		return "c.name"
+	default: // "created"
+		return "t.id"
+	}
+}
+
+// isPgUniqueViolation reports whether err is a PostgreSQL unique-constraint error.
+func isPgUniqueViolation(err error) bool {
+	var pgErr *pgconn.PgError
+	return errors.As(err, &pgErr) && pgErr.Code == "23505"
+}
+
+// ---------------------------------------------------------------------------
+// TagRepo — implements port.TagRepo
+// ---------------------------------------------------------------------------
+
+// TagRepo handles tag CRUD and file–tag relations.
+type TagRepo struct {
+	pool *pgxpool.Pool
+}
+
+var _ port.TagRepo = (*TagRepo)(nil)
+
+// NewTagRepo creates a TagRepo backed by pool.
+func NewTagRepo(pool *pgxpool.Pool) *TagRepo {
+	return &TagRepo{pool: pool}
+}
+
+// ---------------------------------------------------------------------------
+// List / ListByCategory
+// ---------------------------------------------------------------------------
+
+func (r *TagRepo) List(ctx context.Context, params port.OffsetParams) (*domain.TagOffsetPage, error) {
+	return r.listTags(ctx, params, nil)
+}
+
+func (r *TagRepo) ListByCategory(ctx context.Context, categoryID uuid.UUID, params port.OffsetParams) (*domain.TagOffsetPage, error) {
+	return r.listTags(ctx, params, &categoryID)
+}
+
+func (r *TagRepo) listTags(ctx context.Context, params port.OffsetParams, categoryID *uuid.UUID) (*domain.TagOffsetPage, error) {
+	order := "ASC"
+	if strings.ToLower(params.Order) == "desc" {
+		order = "DESC"
+	}
+	sortCol := tagSortColumn(params.Sort)
+
+	// When sorting by category, break ties within a category by the tag's own
+	// name (same direction), so tags are grouped by category then alphabetical.
+	secondarySort := ""
+	if params.Sort == "category_name" {
+		secondarySort = fmt.Sprintf("t.name %s, ", order)
+	}
+
+	args := []any{}
+	n := 1
+	var conditions []string
+
+	if params.Search != "" {
+		conditions = append(conditions, fmt.Sprintf("lower(t.name) LIKE lower($%d)", n))
+		args = append(args, "%"+params.Search+"%")
+		n++
+	}
+	if categoryID != nil {
+		conditions = append(conditions, fmt.Sprintf("t.category_id = $%d", n))
+		args = append(args, *categoryID)
+		n++
+	}
+	// Restrict to tags the viewer may see (private-by-default), unless admin.
+	if !params.ViewerIsAdmin {
+		var aclCond string
+		aclCond, n, args = aclVisibilityCond("t", objTypeTag, params.ViewerID, n, args)
+		conditions = append(conditions, aclCond)
+	}
+
+	where := ""
+	if len(conditions) > 0 {
+		where = "WHERE " + strings.Join(conditions, " AND ")
+	}
+
+	limit := params.Limit
+	if limit <= 0 {
+		limit = 50
+	}
+	offset := params.Offset
+	if offset < 0 {
+		offset = 0
+	}
+
+	query := fmt.Sprintf(`
+SELECT
+    t.id, t.name, t.notes, t.color,
+    t.category_id,
+    c.name  AS category_name,
+    c.color AS category_color,
+    t.metadata, t.creator_id,
+    u.name  AS creator_name,
+    t.is_public,
+    COUNT(*) OVER() AS total
+FROM data.tags t
+LEFT JOIN data.categories c ON c.id = t.category_id
+JOIN      core.users u ON u.id = t.creator_id
+%s
+ORDER BY %s %s NULLS LAST, %st.id ASC
+LIMIT $%d OFFSET $%d`, where, sortCol, order, secondarySort, n, n+1)
+
+	args = append(args, limit, offset)
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query, args...)
+	if err != nil {
+		return nil, fmt.Errorf("TagRepo.List query: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[tagRowWithTotal])
+	if err != nil {
+		return nil, fmt.Errorf("TagRepo.List scan: %w", err)
+	}
+
+	items := make([]domain.Tag, len(collected))
+	total := 0
+	for i, row := range collected {
+		items[i] = toTag(row.tagRow)
+		total = row.Total
+	}
+	return &domain.TagOffsetPage{
+		Items:  items,
+		Total:  total,
+		Offset: offset,
+		Limit:  limit,
+	}, nil
+}
+
+// ---------------------------------------------------------------------------
+// GetByID
+// ---------------------------------------------------------------------------
+
+func (r *TagRepo) GetByID(ctx context.Context, id uuid.UUID) (*domain.Tag, error) {
+	const query = tagSelectFrom + `
+WHERE t.id = $1`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query, id)
+	if err != nil {
+		return nil, fmt.Errorf("TagRepo.GetByID: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[tagRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("TagRepo.GetByID scan: %w", err)
+	}
+	t := toTag(row)
+	return &t, nil
+}
+
+// ---------------------------------------------------------------------------
+// Create
+// ---------------------------------------------------------------------------
+
+func (r *TagRepo) Create(ctx context.Context, t *domain.Tag) (*domain.Tag, error) {
+	const query = `
+WITH ins AS (
+    INSERT INTO data.tags (name, notes, color, category_id, metadata, creator_id, is_public)
+    VALUES ($1, $2, NULLIF($3, ''), $4, $5, $6, $7)
+    RETURNING *
+)
+SELECT
+    ins.id, ins.name, ins.notes, ins.color,
+    ins.category_id,
+    c.name  AS category_name,
+    c.color AS category_color,
+    ins.metadata, ins.creator_id,
+    u.name  AS creator_name,
+    ins.is_public
+FROM ins
+LEFT JOIN data.categories c ON c.id = ins.category_id
+JOIN      core.users u ON u.id = ins.creator_id`
+
+	var meta any
+	if len(t.Metadata) > 0 {
+		meta = t.Metadata
+	}
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query,
+		t.Name, t.Notes, t.Color, t.CategoryID, meta, t.CreatorID, t.IsPublic)
+	if err != nil {
+		return nil, fmt.Errorf("TagRepo.Create: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[tagRow])
+	if err != nil {
+		if isPgUniqueViolation(err) {
+			return nil, domain.ErrConflict
+		}
+		return nil, fmt.Errorf("TagRepo.Create scan: %w", err)
+	}
+	created := toTag(row)
+	return &created, nil
+}
+
+// ---------------------------------------------------------------------------
+// Update
+// ---------------------------------------------------------------------------
+
+// Update replaces all mutable fields. The caller must merge current values with
+// the patch (read-then-write) before calling this.
+func (r *TagRepo) Update(ctx context.Context, id uuid.UUID, t *domain.Tag) (*domain.Tag, error) {
+	const query = `
+WITH upd AS (
+    UPDATE data.tags SET
+        name        = $2,
+        notes       = $3,
+        color       = NULLIF($4, ''),
+        category_id = $5,
+        metadata    = COALESCE($6, metadata),
+        is_public   = $7
+    WHERE id = $1
+    RETURNING *
+)
+SELECT
+    upd.id, upd.name, upd.notes, upd.color,
+    upd.category_id,
+    c.name  AS category_name,
+    c.color AS category_color,
+    upd.metadata, upd.creator_id,
+    u.name  AS creator_name,
+    upd.is_public
+FROM upd
+LEFT JOIN data.categories c ON c.id = upd.category_id
+JOIN      core.users u ON u.id = upd.creator_id`
+
+	var meta any
+	if len(t.Metadata) > 0 {
+		meta = t.Metadata
+	}
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query,
+		id, t.Name, t.Notes, t.Color, t.CategoryID, meta, t.IsPublic)
+	if err != nil {
+		return nil, fmt.Errorf("TagRepo.Update: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[tagRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		if isPgUniqueViolation(err) {
+			return nil, domain.ErrConflict
+		}
+		return nil, fmt.Errorf("TagRepo.Update scan: %w", err)
+	}
+	updated := toTag(row)
+	return &updated, nil
+}
+
+// ---------------------------------------------------------------------------
+// Delete
+// ---------------------------------------------------------------------------
+
+func (r *TagRepo) Delete(ctx context.Context, id uuid.UUID) error {
+	const query = `DELETE FROM data.tags WHERE id = $1`
+
+	q := connOrTx(ctx, r.pool)
+	ct, err := q.Exec(ctx, query, id)
+	if err != nil {
+		return fmt.Errorf("TagRepo.Delete: %w", err)
+	}
+	if ct.RowsAffected() == 0 {
+		return domain.ErrNotFound
+	}
+	return nil
+}
+
+// ---------------------------------------------------------------------------
+// File–tag operations
+// ---------------------------------------------------------------------------
+
+func (r *TagRepo) ListByFile(ctx context.Context, fileID uuid.UUID) ([]domain.Tag, error) {
+	const query = tagSelectFrom + `
+JOIN data.file_tag ft ON ft.tag_id = t.id
+WHERE ft.file_id = $1
+ORDER BY t.name`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query, fileID)
+	if err != nil {
+		return nil, fmt.Errorf("TagRepo.ListByFile: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[tagRow])
+	if err != nil {
+		return nil, fmt.Errorf("TagRepo.ListByFile scan: %w", err)
+	}
+	tags := make([]domain.Tag, len(collected))
+	for i, row := range collected {
+		tags[i] = toTag(row)
+	}
+	return tags, nil
+}
+
+func (r *TagRepo) AddFileTag(ctx context.Context, fileID, tagID uuid.UUID) error {
+	const query = `
+INSERT INTO data.file_tag (file_id, tag_id) VALUES ($1, $2)
+ON CONFLICT DO NOTHING`
+
+	q := connOrTx(ctx, r.pool)
+	if _, err := q.Exec(ctx, query, fileID, tagID); err != nil {
+		return fmt.Errorf("TagRepo.AddFileTag: %w", err)
+	}
+	return nil
+}
+
+func (r *TagRepo) RemoveFileTag(ctx context.Context, fileID, tagID uuid.UUID) error {
+	const query = `DELETE FROM data.file_tag WHERE file_id = $1 AND tag_id = $2`
+
+	q := connOrTx(ctx, r.pool)
+	if _, err := q.Exec(ctx, query, fileID, tagID); err != nil {
+		return fmt.Errorf("TagRepo.RemoveFileTag: %w", err)
+	}
+	return nil
+}
+
+func (r *TagRepo) SetFileTags(ctx context.Context, fileID uuid.UUID, tagIDs []uuid.UUID) error {
+	q := connOrTx(ctx, r.pool)
+
+	if _, err := q.Exec(ctx,
+		`DELETE FROM data.file_tag WHERE file_id = $1`, fileID); err != nil {
+		return fmt.Errorf("TagRepo.SetFileTags delete: %w", err)
+	}
+	if len(tagIDs) == 0 {
+		return nil
+	}
+
+	placeholders := make([]string, len(tagIDs))
+	args := []any{fileID}
+	for i, tagID := range tagIDs {
+		placeholders[i] = fmt.Sprintf("($1, $%d)", i+2)
+		args = append(args, tagID)
+	}
+	ins := `INSERT INTO data.file_tag (file_id, tag_id) VALUES ` +
+		strings.Join(placeholders, ", ") + ` ON CONFLICT DO NOTHING`
+
+	if _, err := q.Exec(ctx, ins, args...); err != nil {
+		return fmt.Errorf("TagRepo.SetFileTags insert: %w", err)
+	}
+	return nil
+}
+
+func (r *TagRepo) CommonTagsForFiles(ctx context.Context, fileIDs []uuid.UUID) ([]domain.Tag, error) {
+	if len(fileIDs) == 0 {
+		return []domain.Tag{}, nil
+	}
+	return r.queryTagsByPresence(ctx, fileIDs, "=")
+}
+
+func (r *TagRepo) PartialTagsForFiles(ctx context.Context, fileIDs []uuid.UUID) ([]domain.Tag, error) {
+	if len(fileIDs) == 0 {
+		return []domain.Tag{}, nil
+	}
+	return r.queryTagsByPresence(ctx, fileIDs, "<")
+}
+
+func (r *TagRepo) queryTagsByPresence(ctx context.Context, fileIDs []uuid.UUID, op string) ([]domain.Tag, error) {
+	placeholders := make([]string, len(fileIDs))
+	args := make([]any, len(fileIDs)+1)
+	for i, id := range fileIDs {
+		placeholders[i] = fmt.Sprintf("$%d", i+1)
+		args[i] = id
+	}
+	args[len(fileIDs)] = len(fileIDs)
+	n := len(fileIDs) + 1
+
+	query := fmt.Sprintf(`
+SELECT
+    t.id, t.name, t.notes, t.color,
+    t.category_id,
+    c.name  AS category_name,
+    c.color AS category_color,
+    t.metadata, t.creator_id,
+    u.name  AS creator_name,
+    t.is_public
+FROM data.tags t
+JOIN data.file_tag ft ON ft.tag_id = t.id
+LEFT JOIN data.categories c ON c.id = t.category_id
+JOIN      core.users u ON u.id = t.creator_id
+WHERE ft.file_id IN (%s)
+GROUP BY t.id, c.id, u.id
+HAVING COUNT(DISTINCT ft.file_id) %s $%d
+ORDER BY t.name`,
+		strings.Join(placeholders, ", "), op, n)
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query, args...)
+	if err != nil {
+		return nil, fmt.Errorf("TagRepo.queryTagsByPresence: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[tagRow])
+	if err != nil {
+		return nil, fmt.Errorf("TagRepo.queryTagsByPresence scan: %w", err)
+	}
+	tags := make([]domain.Tag, len(collected))
+	for i, row := range collected {
+		tags[i] = toTag(row)
+	}
+	return tags, nil
+}
+
+// ---------------------------------------------------------------------------
+// TagRuleRepo — implements port.TagRuleRepo (separate type to avoid method collision)
+// ---------------------------------------------------------------------------
+
+// TagRuleRepo handles tag-rule CRUD.
+type TagRuleRepo struct {
+	pool *pgxpool.Pool
+}
+
+var _ port.TagRuleRepo = (*TagRuleRepo)(nil)
+
+// NewTagRuleRepo creates a TagRuleRepo backed by pool.
+func NewTagRuleRepo(pool *pgxpool.Pool) *TagRuleRepo {
+	return &TagRuleRepo{pool: pool}
+}
+
+func (r *TagRuleRepo) ListByTag(ctx context.Context, tagID uuid.UUID) ([]domain.TagRule, error) {
+	const query = `
+SELECT
+    tr.when_tag_id,
+    tr.then_tag_id,
+    t.name AS then_tag_name,
+    tr.is_active
+FROM data.tag_rules tr
+JOIN data.tags t ON t.id = tr.then_tag_id
+WHERE tr.when_tag_id = $1
+ORDER BY t.name`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query, tagID)
+	if err != nil {
+		return nil, fmt.Errorf("TagRuleRepo.ListByTag: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[tagRuleRow])
+	if err != nil {
+		return nil, fmt.Errorf("TagRuleRepo.ListByTag scan: %w", err)
+	}
+	rules := make([]domain.TagRule, len(collected))
+	for i, row := range collected {
+		rules[i] = toTagRule(row)
+	}
+	return rules, nil
+}
+
+func (r *TagRuleRepo) Create(ctx context.Context, rule domain.TagRule) (*domain.TagRule, error) {
+	const query = `
+WITH ins AS (
+    INSERT INTO data.tag_rules (when_tag_id, then_tag_id, is_active)
+    VALUES ($1, $2, $3)
+    RETURNING *
+)
+SELECT ins.when_tag_id, ins.then_tag_id, t.name AS then_tag_name, ins.is_active
+FROM ins
+JOIN data.tags t ON t.id = ins.then_tag_id`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, query, rule.WhenTagID, rule.ThenTagID, rule.IsActive)
+	if err != nil {
+		return nil, fmt.Errorf("TagRuleRepo.Create: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[tagRuleRow])
+	if err != nil {
+		if isPgUniqueViolation(err) {
+			return nil, domain.ErrConflict
+		}
+		return nil, fmt.Errorf("TagRuleRepo.Create scan: %w", err)
+	}
+	result := toTagRule(row)
+	return &result, nil
+}
+
+func (r *TagRuleRepo) SetActive(ctx context.Context, whenTagID, thenTagID uuid.UUID, active, applyToExisting bool) error {
+	const updateQuery = `
+UPDATE data.tag_rules SET is_active = $3
+WHERE when_tag_id = $1 AND then_tag_id = $2`
+
+	q := connOrTx(ctx, r.pool)
+	ct, err := q.Exec(ctx, updateQuery, whenTagID, thenTagID, active)
+	if err != nil {
+		return fmt.Errorf("TagRuleRepo.SetActive: %w", err)
+	}
+	if ct.RowsAffected() == 0 {
+		return domain.ErrNotFound
+	}
+
+	if !active || !applyToExisting {
+		return nil
+	}
+
+	// Retroactively apply the full transitive expansion of thenTagID to all
+	// files that already carry whenTagID. The recursive CTE walks active rules
+	// starting from thenTagID (mirrors the Go expandTagSet BFS).
+	const retroQuery = `
+WITH RECURSIVE expansion(tag_id) AS (
+    SELECT $2::uuid
+    UNION
+    SELECT r.then_tag_id
+    FROM data.tag_rules r
+    JOIN expansion e ON r.when_tag_id = e.tag_id
+    WHERE r.is_active = true
+)
+INSERT INTO data.file_tag (file_id, tag_id)
+SELECT ft.file_id, e.tag_id
+FROM data.file_tag ft
+CROSS JOIN expansion e
+WHERE ft.tag_id = $1
+ON CONFLICT DO NOTHING`
+
+	if _, err := q.Exec(ctx, retroQuery, whenTagID, thenTagID); err != nil {
+		return fmt.Errorf("TagRuleRepo.SetActive retroactive apply: %w", err)
+	}
+	return nil
+}
+
+func (r *TagRuleRepo) Delete(ctx context.Context, whenTagID, thenTagID uuid.UUID) error {
+	const query = `
+DELETE FROM data.tag_rules
+WHERE when_tag_id = $1 AND then_tag_id = $2`
+
+	q := connOrTx(ctx, r.pool)
+	ct, err := q.Exec(ctx, query, whenTagID, thenTagID)
+	if err != nil {
+		return fmt.Errorf("TagRuleRepo.Delete: %w", err)
+	}
+	if ct.RowsAffected() == 0 {
+		return domain.ErrNotFound
+	}
+	return nil
+}

backend/internal/db/postgres/user_repo.go

@@ -0,0 +1,196 @@
+package postgres
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"tanabata/backend/internal/db"
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+// userRow matches the columns returned by every user SELECT.
+type userRow struct {
+	ID        int16  `db:"id"`
+	Name      string `db:"name"`
+	Password  string `db:"password"`
+	IsAdmin   bool   `db:"is_admin"`
+	CanCreate bool   `db:"can_create"`
+	IsBlocked bool   `db:"is_blocked"`
+}
+
+// userRowWithTotal extends userRow with a window-function total for List.
+type userRowWithTotal struct {
+	userRow
+	Total int `db:"total"`
+}
+
+func toUser(r userRow) domain.User {
+	return domain.User{
+		ID:        r.ID,
+		Name:      r.Name,
+		Password:  r.Password,
+		IsAdmin:   r.IsAdmin,
+		CanCreate: r.CanCreate,
+		IsBlocked: r.IsBlocked,
+	}
+}
+
+// userSortColumn whitelists valid sort keys to prevent SQL injection.
+var userSortColumn = map[string]string{
+	"name": "name",
+	"id":   "id",
+}
+
+// UserRepo implements port.UserRepo using PostgreSQL.
+type UserRepo struct {
+	pool *pgxpool.Pool
+}
+
+// NewUserRepo creates a UserRepo backed by pool.
+func NewUserRepo(pool *pgxpool.Pool) *UserRepo {
+	return &UserRepo{pool: pool}
+}
+
+var _ port.UserRepo = (*UserRepo)(nil)
+
+func (r *UserRepo) List(ctx context.Context, params port.OffsetParams) (*domain.UserPage, error) {
+	col, ok := userSortColumn[params.Sort]
+	if !ok {
+		col = "id"
+	}
+	ord := "ASC"
+	if params.Order == "desc" {
+		ord = "DESC"
+	}
+	limit := db.ClampLimit(params.Limit, 50, 200)
+	offset := db.ClampOffset(params.Offset)
+
+	sql := fmt.Sprintf(`
+		SELECT id, name, password, is_admin, can_create, is_blocked,
+		       COUNT(*) OVER() AS total
+		FROM core.users
+		ORDER BY %s %s
+		LIMIT $1 OFFSET $2`, col, ord)
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql, limit, offset)
+	if err != nil {
+		return nil, fmt.Errorf("UserRepo.List: %w", err)
+	}
+	collected, err := pgx.CollectRows(rows, pgx.RowToStructByName[userRowWithTotal])
+	if err != nil {
+		return nil, fmt.Errorf("UserRepo.List scan: %w", err)
+	}
+
+	page := &domain.UserPage{Offset: offset, Limit: limit}
+	if len(collected) > 0 {
+		page.Total = collected[0].Total
+	}
+	page.Items = make([]domain.User, len(collected))
+	for i, row := range collected {
+		page.Items[i] = toUser(row.userRow)
+	}
+	return page, nil
+}
+
+func (r *UserRepo) GetByID(ctx context.Context, id int16) (*domain.User, error) {
+	const sql = `
+		SELECT id, name, password, is_admin, can_create, is_blocked
+		FROM core.users WHERE id = $1`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql, id)
+	if err != nil {
+		return nil, fmt.Errorf("UserRepo.GetByID: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[userRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("UserRepo.GetByID scan: %w", err)
+	}
+	u := toUser(row)
+	return &u, nil
+}
+
+func (r *UserRepo) GetByName(ctx context.Context, name string) (*domain.User, error) {
+	const sql = `
+		SELECT id, name, password, is_admin, can_create, is_blocked
+		FROM core.users WHERE name = $1`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql, name)
+	if err != nil {
+		return nil, fmt.Errorf("UserRepo.GetByName: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[userRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("UserRepo.GetByName scan: %w", err)
+	}
+	u := toUser(row)
+	return &u, nil
+}
+
+func (r *UserRepo) Create(ctx context.Context, u *domain.User) (*domain.User, error) {
+	const sql = `
+		INSERT INTO core.users (name, password, is_admin, can_create)
+		VALUES ($1, $2, $3, $4)
+		RETURNING id, name, password, is_admin, can_create, is_blocked`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql, u.Name, u.Password, u.IsAdmin, u.CanCreate)
+	if err != nil {
+		return nil, fmt.Errorf("UserRepo.Create: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[userRow])
+	if err != nil {
+		return nil, fmt.Errorf("UserRepo.Create scan: %w", err)
+	}
+	created := toUser(row)
+	return &created, nil
+}
+
+func (r *UserRepo) Update(ctx context.Context, id int16, u *domain.User) (*domain.User, error) {
+	const sql = `
+		UPDATE core.users
+		SET name = $2, password = $3, is_admin = $4, can_create = $5, is_blocked = $6
+		WHERE id = $1
+		RETURNING id, name, password, is_admin, can_create, is_blocked`
+
+	q := connOrTx(ctx, r.pool)
+	rows, err := q.Query(ctx, sql, id, u.Name, u.Password, u.IsAdmin, u.CanCreate, u.IsBlocked)
+	if err != nil {
+		return nil, fmt.Errorf("UserRepo.Update: %w", err)
+	}
+	row, err := pgx.CollectOneRow(rows, pgx.RowToStructByName[userRow])
+	if err != nil {
+		if errors.Is(err, pgx.ErrNoRows) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("UserRepo.Update scan: %w", err)
+	}
+	updated := toUser(row)
+	return &updated, nil
+}
+
+func (r *UserRepo) Delete(ctx context.Context, id int16) error {
+	const sql = `DELETE FROM core.users WHERE id = $1`
+	q := connOrTx(ctx, r.pool)
+	tag, err := q.Exec(ctx, sql, id)
+	if err != nil {
+		return fmt.Errorf("UserRepo.Delete: %w", err)
+	}
+	if tag.RowsAffected() == 0 {
+		return domain.ErrNotFound
+	}
+	return nil
+}

backend/internal/domain/acl.go

@@ -0,0 +1,19 @@
+package domain
+
+import "github.com/google/uuid"
+
+// ObjectType is a reference entity (file, tag, category, pool).
+type ObjectType struct {
+	ID   int16
+	Name string
+}
+
+// Permission represents a per-object access entry for a user.
+type Permission struct {
+	UserID       int16
+	UserName     string // denormalized
+	ObjectTypeID int16
+	ObjectID     uuid.UUID
+	CanView      bool
+	CanEdit      bool
+}

backend/internal/domain/audit.go

@@ -0,0 +1,46 @@
+package domain
+
+import (
+	"encoding/json"
+	"time"
+
+	"github.com/google/uuid"
+)
+
+// ActionType is a reference entity for auditable user actions.
+type ActionType struct {
+	ID   int16
+	Name string
+}
+
+// AuditEntry is a single audit log record.
+type AuditEntry struct {
+	ID          int64
+	UserID      int16
+	UserName    string // denormalized
+	Action      string // action type name, e.g. "file_create"
+	ObjectType  *string
+	ObjectID    *uuid.UUID
+	Details     json.RawMessage
+	PerformedAt time.Time
+}
+
+// AuditPage is an offset-based page of audit log entries.
+type AuditPage struct {
+	Items  []AuditEntry
+	Total  int
+	Offset int
+	Limit  int
+}
+
+// AuditFilter holds filter parameters for querying the audit log.
+type AuditFilter struct {
+	UserID     *int16
+	Action     string
+	ObjectType string
+	ObjectID   *uuid.UUID
+	From       *time.Time
+	To         *time.Time
+	Offset     int
+	Limit      int
+}

backend/internal/domain/category.go

@@ -0,0 +1,29 @@
+package domain
+
+import (
+	"encoding/json"
+	"time"
+
+	"github.com/google/uuid"
+)
+
+// Category is a logical grouping of tags.
+type Category struct {
+	ID          uuid.UUID
+	Name        string
+	Notes       *string
+	Color       *string // 6-char hex
+	Metadata    json.RawMessage
+	CreatorID   int16
+	CreatorName string // denormalized
+	IsPublic    bool
+	CreatedAt   time.Time // extracted from UUID v7 via UUIDCreatedAt
+}
+
+// CategoryOffsetPage is an offset-based page of categories.
+type CategoryOffsetPage struct {
+	Items  []Category
+	Total  int
+	Offset int
+	Limit  int
+}

backend/internal/domain/context.go

@@ -0,0 +1,32 @@
+package domain
+
+import "context"
+
+type ctxKey int
+
+const userKey ctxKey = iota
+
+type contextUser struct {
+	ID        int16
+	IsAdmin   bool
+	SessionID int
+}
+
+// WithUser stores user identity and current session ID in ctx.
+func WithUser(ctx context.Context, userID int16, isAdmin bool, sessionID int) context.Context {
+	return context.WithValue(ctx, userKey, contextUser{
+		ID:        userID,
+		IsAdmin:   isAdmin,
+		SessionID: sessionID,
+	})
+}
+
+// UserFromContext retrieves user identity from ctx.
+// Returns zero values if no user is stored.
+func UserFromContext(ctx context.Context) (userID int16, isAdmin bool, sessionID int) {
+	u, ok := ctx.Value(userKey).(contextUser)
+	if !ok {
+		return 0, false, 0
+	}
+	return u.ID, u.IsAdmin, u.SessionID
+}

backend/internal/domain/errors.go

@@ -0,0 +1,21 @@
+package domain
+
+// DomainError is a typed domain error with a stable machine-readable code.
+// Handlers map these codes to HTTP status codes.
+type DomainError struct {
+	code    string
+	message string
+}
+
+func (e *DomainError) Error() string { return e.message }
+func (e *DomainError) Code() string  { return e.code }
+
+// Sentinel domain errors. Use errors.Is(err, domain.ErrNotFound) for matching.
+var (
+	ErrNotFound        = &DomainError{"not_found", "not found"}
+	ErrForbidden       = &DomainError{"forbidden", "forbidden"}
+	ErrUnauthorized    = &DomainError{"unauthorized", "unauthorized"}
+	ErrConflict        = &DomainError{"conflict", "conflict"}
+	ErrValidation      = &DomainError{"validation_error", "validation error"}
+	ErrUnsupportedMIME = &DomainError{"unsupported_mime", "unsupported MIME type"}
+)

backend/internal/domain/file.go

@@ -0,0 +1,73 @@
+package domain
+
+import (
+	"encoding/json"
+	"time"
+
+	"github.com/google/uuid"
+)
+
+// MIMEType holds MIME whitelist data.
+type MIMEType struct {
+	ID        int16
+	Name      string
+	Extension string
+}
+
+// File represents a managed file record.
+type File struct {
+	ID              uuid.UUID
+	OriginalName    *string
+	MIMEType        string // denormalized from core.mime_types
+	MIMEExtension   string // denormalized from core.mime_types
+	ContentDatetime time.Time
+	Notes           *string
+	Metadata        json.RawMessage
+	EXIF            json.RawMessage
+	PHash           *int64
+	CreatorID       int16
+	CreatorName     string // denormalized from core.users
+	IsPublic        bool
+	IsDeleted       bool
+	CreatedAt       time.Time // extracted from UUID v7 via UUIDCreatedAt
+	Tags            []Tag     // loaded with the file
+}
+
+// FileListParams holds all parameters for listing/filtering files.
+type FileListParams struct {
+	// Pagination
+	Cursor    string
+	Direction string // "forward" or "backward"
+	Anchor    *uuid.UUID
+	Limit     int
+
+	// Sorting
+	Sort  string // "content_datetime" | "created" | "original_name" | "mime"
+	Order string // "asc" | "desc"
+
+	// Filtering
+	Filter string // filter DSL expression
+	Search string // substring match on original_name
+	Trash  bool   // if true, return only soft-deleted files
+
+	// Visibility — populated by the service from the request context. When
+	// ViewerIsAdmin is false the repository restricts results to files the
+	// viewer may see (public, owned, or explicitly granted).
+	ViewerID      int16
+	ViewerIsAdmin bool
+}
+
+// FilePage is the result of a cursor-based file listing.
+type FilePage struct {
+	Items      []File
+	NextCursor *string
+	PrevCursor *string
+}
+
+// UUIDCreatedAt extracts the creation timestamp embedded in a UUID v7.
+// UUID v7 stores Unix milliseconds in the most-significant 48 bits.
+func UUIDCreatedAt(id uuid.UUID) time.Time {
+	ms := int64(id[0])<<40 | int64(id[1])<<32 | int64(id[2])<<24 |
+		int64(id[3])<<16 | int64(id[4])<<8 | int64(id[5])
+	return time.Unix(ms/1000, (ms%1000)*int64(time.Millisecond)).UTC()
+}

backend/internal/domain/pool.go

@@ -0,0 +1,41 @@
+package domain
+
+import (
+	"encoding/json"
+	"time"
+
+	"github.com/google/uuid"
+)
+
+// Pool is an ordered collection of files.
+type Pool struct {
+	ID          uuid.UUID
+	Name        string
+	Notes       *string
+	Metadata    json.RawMessage
+	CreatorID   int16
+	CreatorName string // denormalized
+	IsPublic    bool
+	FileCount   int
+	CreatedAt   time.Time // extracted from UUID v7 via UUIDCreatedAt
+}
+
+// PoolFile is a File with its ordering position within a pool.
+type PoolFile struct {
+	File
+	Position int
+}
+
+// PoolFilePage is the result of a cursor-based pool file listing.
+type PoolFilePage struct {
+	Items      []PoolFile
+	NextCursor *string
+}
+
+// PoolOffsetPage is an offset-based page of pools.
+type PoolOffsetPage struct {
+	Items  []Pool
+	Total  int
+	Offset int
+	Limit  int
+}

backend/internal/domain/tag.go

@@ -0,0 +1,41 @@
+package domain
+
+import (
+	"encoding/json"
+	"time"
+
+	"github.com/google/uuid"
+)
+
+// Tag represents a file label.
+type Tag struct {
+	ID            uuid.UUID
+	Name          string
+	Notes         *string
+	Color         *string // 6-char hex, e.g. "5DCAA5"
+	CategoryID    *uuid.UUID
+	CategoryName  *string // denormalized
+	CategoryColor *string // denormalized
+	Metadata      json.RawMessage
+	CreatorID     int16
+	CreatorName   string // denormalized
+	IsPublic      bool
+	CreatedAt     time.Time // extracted from UUID v7 via UUIDCreatedAt
+}
+
+// TagRule defines an auto-tagging rule: when WhenTagID is applied,
+// ThenTagID is automatically applied as well.
+type TagRule struct {
+	WhenTagID   uuid.UUID
+	ThenTagID   uuid.UUID
+	ThenTagName string // denormalized
+	IsActive    bool
+}
+
+// TagOffsetPage is an offset-based page of tags.
+type TagOffsetPage struct {
+	Items  []Tag
+	Total  int
+	Offset int
+	Limit  int
+}

backend/internal/domain/user.go

@@ -0,0 +1,39 @@
+package domain
+
+import "time"
+
+// User is an application user.
+type User struct {
+	ID        int16
+	Name      string
+	Password  string // bcrypt hash; only populated when needed for auth
+	IsAdmin   bool
+	CanCreate bool
+	IsBlocked bool
+}
+
+// Session is an active user session.
+type Session struct {
+	ID           int
+	TokenHash    string
+	UserID       int16
+	UserAgent    string
+	StartedAt    time.Time
+	ExpiresAt    *time.Time
+	LastActivity time.Time
+	IsCurrent    bool // true when this session matches the caller's token
+}
+
+// UserPage is an offset-based page of users.
+type UserPage struct {
+	Items  []User
+	Total  int
+	Offset int
+	Limit  int
+}
+
+// SessionList is a list of sessions with a total count.
+type SessionList struct {
+	Items []Session
+	Total int
+}

backend/internal/handler/acl_handler.go

@@ -0,0 +1,146 @@
+package handler
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/service"
+)
+
+// objectTypeIDs maps the URL segment to the object_type PK in core.object_types.
+// Row order matches 007_seed_data.sql: file=1, tag=2, category=3, pool=4.
+var objectTypeIDs = map[string]int16{
+	"file":     1,
+	"tag":      2,
+	"category": 3,
+	"pool":     4,
+}
+
+// ACLHandler handles GET/PUT /acl/:object_type/:object_id.
+type ACLHandler struct {
+	aclSvc *service.ACLService
+}
+
+// NewACLHandler creates an ACLHandler.
+func NewACLHandler(aclSvc *service.ACLService) *ACLHandler {
+	return &ACLHandler{aclSvc: aclSvc}
+}
+
+// ---------------------------------------------------------------------------
+// Response type
+// ---------------------------------------------------------------------------
+
+type permissionJSON struct {
+	UserID   int16  `json:"user_id"`
+	UserName string `json:"user_name"`
+	CanView  bool   `json:"can_view"`
+	CanEdit  bool   `json:"can_edit"`
+}
+
+func toPermissionJSON(p domain.Permission) permissionJSON {
+	return permissionJSON{
+		UserID:   p.UserID,
+		UserName: p.UserName,
+		CanView:  p.CanView,
+		CanEdit:  p.CanEdit,
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+func parseACLPath(c *gin.Context) (objectTypeID int16, objectID uuid.UUID, ok bool) {
+	typeStr := c.Param("object_type")
+	id, exists := objectTypeIDs[typeStr]
+	if !exists {
+		respondError(c, domain.ErrValidation)
+		return 0, uuid.UUID{}, false
+	}
+
+	objectID, err := uuid.Parse(c.Param("object_id"))
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return 0, uuid.UUID{}, false
+	}
+
+	return id, objectID, true
+}
+
+// ---------------------------------------------------------------------------
+// GET /acl/:object_type/:object_id
+// ---------------------------------------------------------------------------
+
+func (h *ACLHandler) GetPermissions(c *gin.Context) {
+	objectTypeID, objectID, ok := parseACLPath(c)
+	if !ok {
+		return
+	}
+
+	userID, isAdmin, _ := domain.UserFromContext(c.Request.Context())
+	perms, err := h.aclSvc.GetPermissions(c.Request.Context(), userID, isAdmin, objectTypeID, objectID)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	out := make([]permissionJSON, len(perms))
+	for i, p := range perms {
+		out[i] = toPermissionJSON(p)
+	}
+	respondJSON(c, http.StatusOK, out)
+}
+
+// ---------------------------------------------------------------------------
+// PUT /acl/:object_type/:object_id
+// ---------------------------------------------------------------------------
+
+func (h *ACLHandler) SetPermissions(c *gin.Context) {
+	objectTypeID, objectID, ok := parseACLPath(c)
+	if !ok {
+		return
+	}
+
+	var body struct {
+		Permissions []struct {
+			UserID  int16 `json:"user_id"  binding:"required"`
+			CanView bool  `json:"can_view"`
+			CanEdit bool  `json:"can_edit"`
+		} `json:"permissions" binding:"required"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	perms := make([]domain.Permission, len(body.Permissions))
+	for i, p := range body.Permissions {
+		perms[i] = domain.Permission{
+			UserID:  p.UserID,
+			CanView: p.CanView,
+			CanEdit: p.CanEdit,
+		}
+	}
+
+	userID, isAdmin, _ := domain.UserFromContext(c.Request.Context())
+	if err := h.aclSvc.SetPermissions(c.Request.Context(), userID, isAdmin, objectTypeID, objectID, perms); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	// Re-read to return the stored permissions (with UserName denormalized).
+	stored, err := h.aclSvc.GetPermissions(c.Request.Context(), userID, isAdmin, objectTypeID, objectID)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	out := make([]permissionJSON, len(stored))
+	for i, p := range stored {
+		out[i] = toPermissionJSON(p)
+	}
+	respondJSON(c, http.StatusOK, out)
+}

backend/internal/handler/audit_handler.go

@@ -0,0 +1,120 @@
+package handler
+
+import (
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/service"
+)
+
+// AuditHandler handles GET /audit.
+type AuditHandler struct {
+	auditSvc *service.AuditService
+}
+
+// NewAuditHandler creates an AuditHandler.
+func NewAuditHandler(auditSvc *service.AuditService) *AuditHandler {
+	return &AuditHandler{auditSvc: auditSvc}
+}
+
+// ---------------------------------------------------------------------------
+// Response type
+// ---------------------------------------------------------------------------
+
+type auditEntryJSON struct {
+	ID          int64   `json:"id"`
+	UserID      int16   `json:"user_id"`
+	UserName    string  `json:"user_name"`
+	Action      string  `json:"action"`
+	ObjectType  *string `json:"object_type"`
+	ObjectID    *string `json:"object_id"`
+	PerformedAt string  `json:"performed_at"`
+}
+
+func toAuditEntryJSON(e domain.AuditEntry) auditEntryJSON {
+	j := auditEntryJSON{
+		ID:          e.ID,
+		UserID:      e.UserID,
+		UserName:    e.UserName,
+		Action:      e.Action,
+		ObjectType:  e.ObjectType,
+		PerformedAt: e.PerformedAt.UTC().Format(time.RFC3339),
+	}
+	if e.ObjectID != nil {
+		s := e.ObjectID.String()
+		j.ObjectID = &s
+	}
+	return j
+}
+
+// ---------------------------------------------------------------------------
+// GET /audit  (admin)
+// ---------------------------------------------------------------------------
+
+func (h *AuditHandler) List(c *gin.Context) {
+	if !requireAdmin(c) {
+		return
+	}
+
+	filter := domain.AuditFilter{}
+
+	if s := c.Query("limit"); s != "" {
+		if n, err := strconv.Atoi(s); err == nil {
+			filter.Limit = n
+		}
+	}
+	if s := c.Query("offset"); s != "" {
+		if n, err := strconv.Atoi(s); err == nil {
+			filter.Offset = n
+		}
+	}
+	if s := c.Query("user_id"); s != "" {
+		if n, err := strconv.ParseInt(s, 10, 16); err == nil {
+			id := int16(n)
+			filter.UserID = &id
+		}
+	}
+	if s := c.Query("action"); s != "" {
+		filter.Action = s
+	}
+	if s := c.Query("object_type"); s != "" {
+		filter.ObjectType = s
+	}
+	if s := c.Query("object_id"); s != "" {
+		if id, err := uuid.Parse(s); err == nil {
+			filter.ObjectID = &id
+		}
+	}
+	if s := c.Query("from"); s != "" {
+		if t, err := time.Parse(time.RFC3339, s); err == nil {
+			filter.From = &t
+		}
+	}
+	if s := c.Query("to"); s != "" {
+		if t, err := time.Parse(time.RFC3339, s); err == nil {
+			filter.To = &t
+		}
+	}
+
+	page, err := h.auditSvc.Query(c.Request.Context(), filter)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	items := make([]auditEntryJSON, len(page.Items))
+	for i, e := range page.Items {
+		items[i] = toAuditEntryJSON(e)
+	}
+	respondJSON(c, http.StatusOK, gin.H{
+		"items":  items,
+		"total":  page.Total,
+		"offset": page.Offset,
+		"limit":  page.Limit,
+	})
+}

backend/internal/handler/auth_handler.go

@@ -0,0 +1,140 @@
+package handler
+
+import (
+	"net/http"
+	"strconv"
+
+	"github.com/gin-gonic/gin"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/service"
+)
+
+// AuthHandler handles all /auth endpoints.
+type AuthHandler struct {
+	authSvc *service.AuthService
+}
+
+// NewAuthHandler creates an AuthHandler backed by authSvc.
+func NewAuthHandler(authSvc *service.AuthService) *AuthHandler {
+	return &AuthHandler{authSvc: authSvc}
+}
+
+// Login handles POST /auth/login.
+func (h *AuthHandler) Login(c *gin.Context) {
+	var req struct {
+		Name     string `json:"name"     binding:"required"`
+		Password string `json:"password" binding:"required"`
+	}
+	if err := c.ShouldBindJSON(&req); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	pair, err := h.authSvc.Login(c.Request.Context(), req.Name, req.Password, c.GetHeader("User-Agent"))
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	respondJSON(c, http.StatusOK, gin.H{
+		"access_token":  pair.AccessToken,
+		"refresh_token": pair.RefreshToken,
+		"expires_in":    pair.ExpiresIn,
+	})
+}
+
+// Refresh handles POST /auth/refresh.
+func (h *AuthHandler) Refresh(c *gin.Context) {
+	var req struct {
+		RefreshToken string `json:"refresh_token" binding:"required"`
+	}
+	if err := c.ShouldBindJSON(&req); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	pair, err := h.authSvc.Refresh(c.Request.Context(), req.RefreshToken, c.GetHeader("User-Agent"))
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	respondJSON(c, http.StatusOK, gin.H{
+		"access_token":  pair.AccessToken,
+		"refresh_token": pair.RefreshToken,
+		"expires_in":    pair.ExpiresIn,
+	})
+}
+
+// Logout handles POST /auth/logout. Requires authentication.
+func (h *AuthHandler) Logout(c *gin.Context) {
+	_, _, sessionID := domain.UserFromContext(c.Request.Context())
+
+	if err := h.authSvc.Logout(c.Request.Context(), sessionID); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	c.Status(http.StatusNoContent)
+}
+
+// ListSessions handles GET /auth/sessions. Requires authentication.
+func (h *AuthHandler) ListSessions(c *gin.Context) {
+	userID, _, sessionID := domain.UserFromContext(c.Request.Context())
+
+	list, err := h.authSvc.ListSessions(c.Request.Context(), userID, sessionID)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	type sessionItem struct {
+		ID           int    `json:"id"`
+		UserAgent    string `json:"user_agent"`
+		StartedAt    string `json:"started_at"`
+		ExpiresAt    any    `json:"expires_at"`
+		LastActivity string `json:"last_activity"`
+		IsCurrent    bool   `json:"is_current"`
+	}
+
+	items := make([]sessionItem, len(list.Items))
+	for i, s := range list.Items {
+		var expiresAt any
+		if s.ExpiresAt != nil {
+			expiresAt = s.ExpiresAt.Format("2006-01-02T15:04:05Z07:00")
+		}
+		items[i] = sessionItem{
+			ID:           s.ID,
+			UserAgent:    s.UserAgent,
+			StartedAt:    s.StartedAt.Format("2006-01-02T15:04:05Z07:00"),
+			ExpiresAt:    expiresAt,
+			LastActivity: s.LastActivity.Format("2006-01-02T15:04:05Z07:00"),
+			IsCurrent:    s.IsCurrent,
+		}
+	}
+
+	respondJSON(c, http.StatusOK, gin.H{
+		"items": items,
+		"total": list.Total,
+	})
+}
+
+// TerminateSession handles DELETE /auth/sessions/:id. Requires authentication.
+func (h *AuthHandler) TerminateSession(c *gin.Context) {
+	idStr := c.Param("id")
+	id, err := strconv.Atoi(idStr)
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	userID, isAdmin, _ := domain.UserFromContext(c.Request.Context())
+
+	if err := h.authSvc.TerminateSession(c.Request.Context(), userID, isAdmin, id); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	c.Status(http.StatusNoContent)
+}

backend/internal/handler/category_handler.go

@@ -0,0 +1,235 @@
+package handler
+
+import (
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/service"
+)
+
+// CategoryHandler handles all /categories endpoints.
+type CategoryHandler struct {
+	categorySvc *service.CategoryService
+}
+
+// NewCategoryHandler creates a CategoryHandler.
+func NewCategoryHandler(categorySvc *service.CategoryService) *CategoryHandler {
+	return &CategoryHandler{categorySvc: categorySvc}
+}
+
+// ---------------------------------------------------------------------------
+// Response types
+// ---------------------------------------------------------------------------
+
+type categoryJSON struct {
+	ID          string  `json:"id"`
+	Name        string  `json:"name"`
+	Notes       *string `json:"notes"`
+	Color       *string `json:"color"`
+	CreatorID   int16   `json:"creator_id"`
+	CreatorName string  `json:"creator_name"`
+	IsPublic    bool    `json:"is_public"`
+	CreatedAt   string  `json:"created_at"`
+}
+
+func toCategoryJSON(c domain.Category) categoryJSON {
+	return categoryJSON{
+		ID:          c.ID.String(),
+		Name:        c.Name,
+		Notes:       c.Notes,
+		Color:       c.Color,
+		CreatorID:   c.CreatorID,
+		CreatorName: c.CreatorName,
+		IsPublic:    c.IsPublic,
+		CreatedAt:   c.CreatedAt.UTC().Format("2006-01-02T15:04:05Z"),
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+func parseCategoryID(c *gin.Context) (uuid.UUID, bool) {
+	id, err := uuid.Parse(c.Param("category_id"))
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return uuid.UUID{}, false
+	}
+	return id, true
+}
+
+// ---------------------------------------------------------------------------
+// GET /categories
+// ---------------------------------------------------------------------------
+
+func (h *CategoryHandler) List(c *gin.Context) {
+	params := parseOffsetParams(c, "created")
+
+	page, err := h.categorySvc.List(c.Request.Context(), params)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	items := make([]categoryJSON, len(page.Items))
+	for i, cat := range page.Items {
+		items[i] = toCategoryJSON(cat)
+	}
+	respondJSON(c, http.StatusOK, gin.H{
+		"items":  items,
+		"total":  page.Total,
+		"offset": page.Offset,
+		"limit":  page.Limit,
+	})
+}
+
+// ---------------------------------------------------------------------------
+// POST /categories
+// ---------------------------------------------------------------------------
+
+func (h *CategoryHandler) Create(c *gin.Context) {
+	var body struct {
+		Name     string  `json:"name"      binding:"required"`
+		Notes    *string `json:"notes"`
+		Color    *string `json:"color"`
+		IsPublic *bool   `json:"is_public"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	created, err := h.categorySvc.Create(c.Request.Context(), service.CategoryParams{
+		Name:     body.Name,
+		Notes:    body.Notes,
+		Color:    body.Color,
+		IsPublic: body.IsPublic,
+	})
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	respondJSON(c, http.StatusCreated, toCategoryJSON(*created))
+}
+
+// ---------------------------------------------------------------------------
+// GET /categories/:category_id
+// ---------------------------------------------------------------------------
+
+func (h *CategoryHandler) Get(c *gin.Context) {
+	id, ok := parseCategoryID(c)
+	if !ok {
+		return
+	}
+
+	cat, err := h.categorySvc.Get(c.Request.Context(), id)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	respondJSON(c, http.StatusOK, toCategoryJSON(*cat))
+}
+
+// ---------------------------------------------------------------------------
+// PATCH /categories/:category_id
+// ---------------------------------------------------------------------------
+
+func (h *CategoryHandler) Update(c *gin.Context) {
+	id, ok := parseCategoryID(c)
+	if !ok {
+		return
+	}
+
+	// Use a raw map to detect explicitly-null fields.
+	var raw map[string]any
+	if err := c.ShouldBindJSON(&raw); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	params := service.CategoryParams{}
+
+	if v, ok := raw["name"]; ok {
+		if s, ok := v.(string); ok {
+			params.Name = s
+		}
+	}
+	if _, ok := raw["notes"]; ok {
+		if raw["notes"] == nil {
+			empty := ""
+			params.Notes = &empty
+		} else if s, ok := raw["notes"].(string); ok {
+			params.Notes = &s
+		}
+	}
+	if _, ok := raw["color"]; ok {
+		if raw["color"] == nil {
+			empty := ""
+			params.Color = &empty
+		} else if s, ok := raw["color"].(string); ok {
+			params.Color = &s
+		}
+	}
+	if v, ok := raw["is_public"]; ok {
+		if b, ok := v.(bool); ok {
+			params.IsPublic = &b
+		}
+	}
+
+	updated, err := h.categorySvc.Update(c.Request.Context(), id, params)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	respondJSON(c, http.StatusOK, toCategoryJSON(*updated))
+}
+
+// ---------------------------------------------------------------------------
+// DELETE /categories/:category_id
+// ---------------------------------------------------------------------------
+
+func (h *CategoryHandler) Delete(c *gin.Context) {
+	id, ok := parseCategoryID(c)
+	if !ok {
+		return
+	}
+
+	if err := h.categorySvc.Delete(c.Request.Context(), id); err != nil {
+		respondError(c, err)
+		return
+	}
+	c.Status(http.StatusNoContent)
+}
+
+// ---------------------------------------------------------------------------
+// GET /categories/:category_id/tags
+// ---------------------------------------------------------------------------
+
+func (h *CategoryHandler) ListTags(c *gin.Context) {
+	id, ok := parseCategoryID(c)
+	if !ok {
+		return
+	}
+
+	params := parseOffsetParams(c, "created")
+
+	page, err := h.categorySvc.ListTags(c.Request.Context(), id, params)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	items := make([]tagJSON, len(page.Items))
+	for i, t := range page.Items {
+		items[i] = toTagJSON(t)
+	}
+	respondJSON(c, http.StatusOK, gin.H{
+		"items":  items,
+		"total":  page.Total,
+		"offset": page.Offset,
+		"limit":  page.Limit,
+	})
+}

backend/internal/handler/file_handler.go

@@ -0,0 +1,733 @@
+package handler
+
+import (
+	"encoding/json"
+	"fmt"
+	"io"
+	"mime/multipart"
+	"net/http"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/gabriel-vasile/mimetype"
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/service"
+)
+
+// FileHandler handles all /files endpoints.
+type FileHandler struct {
+	fileSvc        *service.FileService
+	tagSvc         *service.TagService
+	maxUploadBytes int64
+}
+
+// NewFileHandler creates a FileHandler. maxUploadBytes caps the size of an
+// uploaded or replacement file.
+func NewFileHandler(fileSvc *service.FileService, tagSvc *service.TagService, maxUploadBytes int64) *FileHandler {
+	return &FileHandler{fileSvc: fileSvc, tagSvc: tagSvc, maxUploadBytes: maxUploadBytes}
+}
+
+// formFileLimited reads the "file" multipart field while bounding how many bytes
+// are read from the request body, then rejects files larger than the configured
+// cap. The body limit guards against a dishonest Content-Length; the Size check
+// gives a clear rejection for an honestly-declared oversized file.
+func (h *FileHandler) formFileLimited(c *gin.Context) (*multipart.FileHeader, bool) {
+	// Allow a little slack above the file cap for multipart framing overhead.
+	c.Request.Body = http.MaxBytesReader(c.Writer, c.Request.Body, h.maxUploadBytes+(1<<20))
+
+	fh, err := c.FormFile("file")
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return nil, false
+	}
+	if fh.Size > h.maxUploadBytes {
+		respondError(c, domain.ErrValidation)
+		return nil, false
+	}
+	return fh, true
+}
+
+// ---------------------------------------------------------------------------
+// Response types
+// ---------------------------------------------------------------------------
+
+type tagJSON struct {
+	ID            string  `json:"id"`
+	Name          string  `json:"name"`
+	Notes         *string `json:"notes"`
+	Color         *string `json:"color"`
+	CategoryID    *string `json:"category_id"`
+	CategoryName  *string `json:"category_name"`
+	CategoryColor *string `json:"category_color"`
+	CreatorID     int16   `json:"creator_id"`
+	CreatorName   string  `json:"creator_name"`
+	IsPublic      bool    `json:"is_public"`
+	CreatedAt     string  `json:"created_at"`
+}
+
+type fileJSON struct {
+	ID              string          `json:"id"`
+	OriginalName    *string         `json:"original_name"`
+	MIMEType        string          `json:"mime_type"`
+	MIMEExtension   string          `json:"mime_extension"`
+	ContentDatetime string          `json:"content_datetime"`
+	Notes           *string         `json:"notes"`
+	Metadata        json.RawMessage `json:"metadata"`
+	EXIF            json.RawMessage `json:"exif"`
+	PHash           *int64          `json:"phash"`
+	CreatorID       int16           `json:"creator_id"`
+	CreatorName     string          `json:"creator_name"`
+	IsPublic        bool            `json:"is_public"`
+	IsDeleted       bool            `json:"is_deleted"`
+	CreatedAt       string          `json:"created_at"`
+	Tags            []tagJSON       `json:"tags"`
+}
+
+func toTagJSON(t domain.Tag) tagJSON {
+	j := tagJSON{
+		ID:            t.ID.String(),
+		Name:          t.Name,
+		Notes:         t.Notes,
+		Color:         t.Color,
+		CategoryName:  t.CategoryName,
+		CategoryColor: t.CategoryColor,
+		CreatorID:     t.CreatorID,
+		CreatorName:   t.CreatorName,
+		IsPublic:      t.IsPublic,
+		CreatedAt:     t.CreatedAt.Format(time.RFC3339),
+	}
+	if t.CategoryID != nil {
+		s := t.CategoryID.String()
+		j.CategoryID = &s
+	}
+	return j
+}
+
+func toFileJSON(f domain.File) fileJSON {
+	tags := make([]tagJSON, len(f.Tags))
+	for i, t := range f.Tags {
+		tags[i] = toTagJSON(t)
+	}
+	exif := f.EXIF
+	if exif == nil {
+		exif = json.RawMessage("{}")
+	}
+	return fileJSON{
+		ID:              f.ID.String(),
+		OriginalName:    f.OriginalName,
+		MIMEType:        f.MIMEType,
+		MIMEExtension:   f.MIMEExtension,
+		ContentDatetime: f.ContentDatetime.Format(time.RFC3339),
+		Notes:           f.Notes,
+		Metadata:        f.Metadata,
+		EXIF:            exif,
+		PHash:           f.PHash,
+		CreatorID:       f.CreatorID,
+		CreatorName:     f.CreatorName,
+		IsPublic:        f.IsPublic,
+		IsDeleted:       f.IsDeleted,
+		CreatedAt:       f.CreatedAt.Format(time.RFC3339),
+		Tags:            tags,
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Helper
+// ---------------------------------------------------------------------------
+
+func parseFileID(c *gin.Context) (uuid.UUID, bool) {
+	id, err := uuid.Parse(c.Param("id"))
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return uuid.UUID{}, false
+	}
+	return id, true
+}
+
+// ---------------------------------------------------------------------------
+// GET /files
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) List(c *gin.Context) {
+	params := domain.FileListParams{
+		Cursor:    c.Query("cursor"),
+		Direction: c.DefaultQuery("direction", "forward"),
+		Sort:      c.DefaultQuery("sort", "created"),
+		Order:     c.DefaultQuery("order", "desc"),
+		Filter:    c.Query("filter"),
+		Search:    c.Query("search"),
+	}
+
+	if limitStr := c.Query("limit"); limitStr != "" {
+		n, err := strconv.Atoi(limitStr)
+		if err != nil || n < 1 || n > 200 {
+			respondError(c, domain.ErrValidation)
+			return
+		}
+		params.Limit = n
+	} else {
+		params.Limit = 50
+	}
+
+	if anchorStr := c.Query("anchor"); anchorStr != "" {
+		id, err := uuid.Parse(anchorStr)
+		if err != nil {
+			respondError(c, domain.ErrValidation)
+			return
+		}
+		params.Anchor = &id
+	}
+
+	if trashStr := c.Query("trash"); trashStr == "true" || trashStr == "1" {
+		params.Trash = true
+	}
+
+	page, err := h.fileSvc.List(c.Request.Context(), params)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	items := make([]fileJSON, len(page.Items))
+	for i, f := range page.Items {
+		items[i] = toFileJSON(f)
+	}
+
+	respondJSON(c, http.StatusOK, gin.H{
+		"items":       items,
+		"next_cursor": page.NextCursor,
+		"prev_cursor": page.PrevCursor,
+	})
+}
+
+// ---------------------------------------------------------------------------
+// POST /files  (multipart upload)
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) Upload(c *gin.Context) {
+	fh, ok := h.formFileLimited(c)
+	if !ok {
+		return
+	}
+
+	src, err := fh.Open()
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	defer src.Close()
+
+	// Detect MIME from actual bytes (ignore client-supplied Content-Type).
+	mt, err := mimetype.DetectReader(src)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	// Rewind by reopening — FormFile gives a multipart.File which supports Seek.
+	if _, err := src.Seek(0, io.SeekStart); err != nil {
+		respondError(c, err)
+		return
+	}
+	mimeStr := strings.SplitN(mt.String(), ";", 2)[0]
+
+	params := service.UploadParams{
+		Reader:   src,
+		MIMEType: mimeStr,
+		IsPublic: c.PostForm("is_public") == "true",
+	}
+
+	if name := fh.Filename; name != "" {
+		params.OriginalName = &name
+	}
+	if notes := c.PostForm("notes"); notes != "" {
+		params.Notes = &notes
+	}
+	if metaStr := c.PostForm("metadata"); metaStr != "" {
+		params.Metadata = json.RawMessage(metaStr)
+	}
+	if dtStr := c.PostForm("content_datetime"); dtStr != "" {
+		t, err := time.Parse(time.RFC3339, dtStr)
+		if err != nil {
+			respondError(c, domain.ErrValidation)
+			return
+		}
+		params.ContentDatetime = &t
+	}
+	if tagIDsStr := c.PostForm("tag_ids"); tagIDsStr != "" {
+		for _, raw := range strings.Split(tagIDsStr, ",") {
+			raw = strings.TrimSpace(raw)
+			if raw == "" {
+				continue
+			}
+			id, err := uuid.Parse(raw)
+			if err != nil {
+				respondError(c, domain.ErrValidation)
+				return
+			}
+			params.TagIDs = append(params.TagIDs, id)
+		}
+	}
+
+	f, err := h.fileSvc.Upload(c.Request.Context(), params)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	respondJSON(c, http.StatusCreated, toFileJSON(*f))
+}
+
+// ---------------------------------------------------------------------------
+// GET /files/:id
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) GetMeta(c *gin.Context) {
+	id, ok := parseFileID(c)
+	if !ok {
+		return
+	}
+
+	f, err := h.fileSvc.Get(c.Request.Context(), id)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	respondJSON(c, http.StatusOK, toFileJSON(*f))
+}
+
+// ---------------------------------------------------------------------------
+// POST /files/:id/views
+// ---------------------------------------------------------------------------
+
+// RecordView logs that the current user viewed the file (activity.file_views).
+func (h *FileHandler) RecordView(c *gin.Context) {
+	id, ok := parseFileID(c)
+	if !ok {
+		return
+	}
+
+	if err := h.fileSvc.RecordView(c.Request.Context(), id); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	c.Status(http.StatusNoContent)
+}
+
+// ---------------------------------------------------------------------------
+// PATCH /files/:id
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) UpdateMeta(c *gin.Context) {
+	id, ok := parseFileID(c)
+	if !ok {
+		return
+	}
+
+	var body struct {
+		OriginalName    *string         `json:"original_name"`
+		ContentDatetime *string         `json:"content_datetime"`
+		Notes           *string         `json:"notes"`
+		Metadata        json.RawMessage `json:"metadata"`
+		IsPublic        *bool           `json:"is_public"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	params := service.UpdateParams{
+		OriginalName: body.OriginalName,
+		Notes:        body.Notes,
+		Metadata:     body.Metadata,
+		IsPublic:     body.IsPublic,
+	}
+	if body.ContentDatetime != nil {
+		t, err := time.Parse(time.RFC3339, *body.ContentDatetime)
+		if err != nil {
+			respondError(c, domain.ErrValidation)
+			return
+		}
+		params.ContentDatetime = &t
+	}
+
+	f, err := h.fileSvc.Update(c.Request.Context(), id, params)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	respondJSON(c, http.StatusOK, toFileJSON(*f))
+}
+
+// ---------------------------------------------------------------------------
+// DELETE /files/:id  (soft-delete)
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) SoftDelete(c *gin.Context) {
+	id, ok := parseFileID(c)
+	if !ok {
+		return
+	}
+
+	if err := h.fileSvc.Delete(c.Request.Context(), id); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	c.Status(http.StatusNoContent)
+}
+
+// ---------------------------------------------------------------------------
+// GET /files/:id/content
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) GetContent(c *gin.Context) {
+	id, ok := parseFileID(c)
+	if !ok {
+		return
+	}
+
+	res, err := h.fileSvc.GetContent(c.Request.Context(), id)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	defer res.Body.Close()
+
+	c.Header("Content-Type", res.MIMEType)
+	c.Header("Cache-Control", "private, max-age=3600")
+	// Default to attachment (download); ?inline=1 serves it for in-tab viewing.
+	disposition := "attachment"
+	if c.Query("inline") == "1" {
+		disposition = "inline"
+	}
+	name := ""
+	if res.OriginalName != nil {
+		name = *res.OriginalName
+		c.Header("Content-Disposition",
+			fmt.Sprintf("%s; filename=%q", disposition, name))
+	}
+
+	// Serve with byte-range support when the body is seekable (it is for the
+	// disk store): http.ServeContent advertises Accept-Ranges and answers Range
+	// requests with 206 Partial Content, which is what lets the browser scrub and
+	// seek within audio/video. Fall back to a plain stream otherwise.
+	if seeker, ok := res.Body.(io.ReadSeeker); ok {
+		http.ServeContent(c.Writer, c.Request, name, time.Time{}, seeker)
+		return
+	}
+	c.Status(http.StatusOK)
+	io.Copy(c.Writer, res.Body) //nolint:errcheck
+}
+
+// ---------------------------------------------------------------------------
+// PUT /files/:id/content  (replace)
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) ReplaceContent(c *gin.Context) {
+	id, ok := parseFileID(c)
+	if !ok {
+		return
+	}
+
+	fh, ok := h.formFileLimited(c)
+	if !ok {
+		return
+	}
+
+	src, err := fh.Open()
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	defer src.Close()
+
+	mt, err := mimetype.DetectReader(src)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	if _, err := src.Seek(0, io.SeekStart); err != nil {
+		respondError(c, err)
+		return
+	}
+	mimeStr := strings.SplitN(mt.String(), ";", 2)[0]
+
+	name := fh.Filename
+	params := service.UploadParams{
+		Reader:       src,
+		MIMEType:     mimeStr,
+		OriginalName: &name,
+	}
+
+	f, err := h.fileSvc.Replace(c.Request.Context(), id, params)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	respondJSON(c, http.StatusOK, toFileJSON(*f))
+}
+
+// ---------------------------------------------------------------------------
+// GET /files/:id/thumbnail
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) GetThumbnail(c *gin.Context) {
+	id, ok := parseFileID(c)
+	if !ok {
+		return
+	}
+
+	rc, err := h.fileSvc.GetThumbnail(c.Request.Context(), id)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	defer rc.Close()
+
+	c.Header("Content-Type", "image/jpeg")
+	c.Header("Cache-Control", "private, max-age=3600")
+	c.Status(http.StatusOK)
+	io.Copy(c.Writer, rc) //nolint:errcheck
+}
+
+// ---------------------------------------------------------------------------
+// GET /files/:id/preview
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) GetPreview(c *gin.Context) {
+	id, ok := parseFileID(c)
+	if !ok {
+		return
+	}
+
+	rc, err := h.fileSvc.GetPreview(c.Request.Context(), id)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	defer rc.Close()
+
+	c.Header("Content-Type", "image/jpeg")
+	c.Header("Cache-Control", "private, max-age=3600")
+	c.Status(http.StatusOK)
+	io.Copy(c.Writer, rc) //nolint:errcheck
+}
+
+// ---------------------------------------------------------------------------
+// POST /files/:id/restore
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) Restore(c *gin.Context) {
+	id, ok := parseFileID(c)
+	if !ok {
+		return
+	}
+
+	f, err := h.fileSvc.Restore(c.Request.Context(), id)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	respondJSON(c, http.StatusOK, toFileJSON(*f))
+}
+
+// ---------------------------------------------------------------------------
+// DELETE /files/:id/permanent
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) PermanentDelete(c *gin.Context) {
+	id, ok := parseFileID(c)
+	if !ok {
+		return
+	}
+
+	if err := h.fileSvc.PermanentDelete(c.Request.Context(), id); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	c.Status(http.StatusNoContent)
+}
+
+// ---------------------------------------------------------------------------
+// POST /files/bulk/tags
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) BulkSetTags(c *gin.Context) {
+	var body struct {
+		FileIDs []string `json:"file_ids" binding:"required"`
+		Action  string   `json:"action"   binding:"required"`
+		TagIDs  []string `json:"tag_ids"  binding:"required"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+	if body.Action != "add" && body.Action != "remove" {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	fileIDs, err := parseUUIDs(body.FileIDs)
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+	tagIDs, err := parseUUIDs(body.TagIDs)
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	applied, err := h.tagSvc.BulkSetTags(c.Request.Context(), fileIDs, body.Action, tagIDs)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	strs := make([]string, len(applied))
+	for i, id := range applied {
+		strs[i] = id.String()
+	}
+	respondJSON(c, http.StatusOK, gin.H{"applied_tag_ids": strs})
+}
+
+// ---------------------------------------------------------------------------
+// POST /files/bulk/delete
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) BulkDelete(c *gin.Context) {
+	var body struct {
+		FileIDs []string `json:"file_ids" binding:"required"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	fileIDs, err := parseUUIDs(body.FileIDs)
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	if err := h.fileSvc.BulkDelete(c.Request.Context(), fileIDs); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	c.Status(http.StatusNoContent)
+}
+
+// ---------------------------------------------------------------------------
+// POST /files/bulk/common-tags
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) CommonTags(c *gin.Context) {
+	var body struct {
+		FileIDs []string `json:"file_ids" binding:"required"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	fileIDs, err := parseUUIDs(body.FileIDs)
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	common, partial, err := h.tagSvc.CommonTags(c.Request.Context(), fileIDs)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	toStrs := func(tags []domain.Tag) []string {
+		s := make([]string, len(tags))
+		for i, t := range tags {
+			s[i] = t.ID.String()
+		}
+		return s
+	}
+
+	respondJSON(c, http.StatusOK, gin.H{
+		"common_tag_ids":  toStrs(common),
+		"partial_tag_ids": toStrs(partial),
+	})
+}
+
+// ---------------------------------------------------------------------------
+// POST /files/import
+// ---------------------------------------------------------------------------
+
+func (h *FileHandler) Import(c *gin.Context) {
+	// Server-side directory import reads arbitrary paths on the host; restrict
+	// it to administrators.
+	if !requireAdmin(c) {
+		return
+	}
+
+	var body struct {
+		Path string `json:"path"`
+	}
+	// Body is optional; ignore bind errors.
+	_ = c.ShouldBindJSON(&body)
+
+	// Stream progress as newline-delimited JSON so the client can render a live
+	// progress bar and per-file status. Headers are deferred until the first
+	// event, so a validation error (bad path, import disabled) raised before any
+	// file is touched can still be returned as a normal JSON error response.
+	flusher, canFlush := c.Writer.(http.Flusher)
+	started := false
+	enc := json.NewEncoder(c.Writer)
+
+	emit := func(ev service.ImportEvent) {
+		if !started {
+			c.Header("Content-Type", "application/x-ndjson")
+			c.Header("Cache-Control", "no-cache")
+			c.Header("X-Accel-Buffering", "no") // don't let a proxy buffer the stream
+			c.Writer.WriteHeader(http.StatusOK)
+			started = true
+		}
+		_ = enc.Encode(ev) // appends a newline
+		if canFlush {
+			flusher.Flush()
+		}
+	}
+
+	if _, err := h.fileSvc.Import(c.Request.Context(), body.Path, emit); err != nil {
+		if !started {
+			respondError(c, err)
+			return
+		}
+		// Headers already sent; surface the failure as a terminal stream event.
+		emit(service.ImportEvent{Type: "error", Reason: err.Error()})
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+func parseUUIDs(strs []string) ([]uuid.UUID, error) {
+	ids := make([]uuid.UUID, 0, len(strs))
+	for _, s := range strs {
+		id, err := uuid.Parse(s)
+		if err != nil {
+			return nil, err
+		}
+		ids = append(ids, id)
+	}
+	return ids, nil
+}

backend/internal/handler/middleware.go

@@ -0,0 +1,66 @@
+package handler
+
+import (
+	"net/http"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/service"
+)
+
+// AuthMiddleware validates Bearer JWTs and injects user identity into context.
+type AuthMiddleware struct {
+	authSvc *service.AuthService
+}
+
+// NewAuthMiddleware creates an AuthMiddleware backed by authSvc.
+func NewAuthMiddleware(authSvc *service.AuthService) *AuthMiddleware {
+	return &AuthMiddleware{authSvc: authSvc}
+}
+
+// Handle returns a Gin handler function that enforces authentication.
+// On success it calls c.Next(); on failure it aborts with 401 JSON.
+func (m *AuthMiddleware) Handle() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		token := bearerToken(c)
+		if token == "" {
+			c.JSON(http.StatusUnauthorized, errorBody{
+				Code:    domain.ErrUnauthorized.Code(),
+				Message: "authorization header missing or malformed",
+			})
+			c.Abort()
+			return
+		}
+
+		claims, err := m.authSvc.ValidateAccessToken(c.Request.Context(), token)
+		if err != nil {
+			c.JSON(http.StatusUnauthorized, errorBody{
+				Code:    domain.ErrUnauthorized.Code(),
+				Message: "invalid or expired token",
+			})
+			c.Abort()
+			return
+		}
+
+		ctx := domain.WithUser(c.Request.Context(), claims.UserID, claims.IsAdmin, claims.SessionID)
+		c.Request = c.Request.WithContext(ctx)
+		c.Next()
+	}
+}
+
+// bearerToken extracts the access token from the Authorization header. As a
+// fallback it accepts an ?access_token= query parameter, but only for GET
+// requests — this lets the browser open media (e.g. /files/{id}/content) via a
+// plain link/new tab, where it can't send the header, without allowing a crafted
+// link to drive a state-changing request.
+func bearerToken(c *gin.Context) string {
+	if raw := c.GetHeader("Authorization"); strings.HasPrefix(raw, "Bearer ") {
+		return strings.TrimPrefix(raw, "Bearer ")
+	}
+	if c.Request.Method == http.MethodGet {
+		return c.Query("access_token")
+	}
+	return ""
+}

backend/internal/handler/pool_handler.go

@@ -0,0 +1,375 @@
+package handler
+
+import (
+	"net/http"
+	"strconv"
+	"time"
+
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+	"tanabata/backend/internal/service"
+)
+
+// PoolHandler handles all /pools endpoints.
+type PoolHandler struct {
+	poolSvc *service.PoolService
+}
+
+// NewPoolHandler creates a PoolHandler.
+func NewPoolHandler(poolSvc *service.PoolService) *PoolHandler {
+	return &PoolHandler{poolSvc: poolSvc}
+}
+
+// ---------------------------------------------------------------------------
+// Response types
+// ---------------------------------------------------------------------------
+
+type poolJSON struct {
+	ID          string  `json:"id"`
+	Name        string  `json:"name"`
+	Notes       *string `json:"notes"`
+	CreatorID   int16   `json:"creator_id"`
+	CreatorName string  `json:"creator_name"`
+	IsPublic    bool    `json:"is_public"`
+	FileCount   int     `json:"file_count"`
+	CreatedAt   string  `json:"created_at"`
+}
+
+type poolFileJSON struct {
+	fileJSON
+	Position int `json:"position"`
+}
+
+func toPoolJSON(p domain.Pool) poolJSON {
+	return poolJSON{
+		ID:          p.ID.String(),
+		Name:        p.Name,
+		Notes:       p.Notes,
+		CreatorID:   p.CreatorID,
+		CreatorName: p.CreatorName,
+		IsPublic:    p.IsPublic,
+		FileCount:   p.FileCount,
+		CreatedAt:   p.CreatedAt.UTC().Format(time.RFC3339),
+	}
+}
+
+func toPoolFileJSON(pf domain.PoolFile) poolFileJSON {
+	return poolFileJSON{
+		fileJSON: toFileJSON(pf.File),
+		Position: pf.Position,
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+func parsePoolID(c *gin.Context) (uuid.UUID, bool) {
+	id, err := uuid.Parse(c.Param("pool_id"))
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return uuid.UUID{}, false
+	}
+	return id, true
+}
+
+func parsePoolFileParams(c *gin.Context) port.PoolFileListParams {
+	limit := 50
+	if s := c.Query("limit"); s != "" {
+		if n, err := strconv.Atoi(s); err == nil && n > 0 && n <= 200 {
+			limit = n
+		}
+	}
+	return port.PoolFileListParams{
+		Cursor: c.Query("cursor"),
+		Limit:  limit,
+		Filter: c.Query("filter"),
+	}
+}
+
+// ---------------------------------------------------------------------------
+// GET /pools
+// ---------------------------------------------------------------------------
+
+func (h *PoolHandler) List(c *gin.Context) {
+	params := parseOffsetParams(c, "created")
+
+	page, err := h.poolSvc.List(c.Request.Context(), params)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	items := make([]poolJSON, len(page.Items))
+	for i, p := range page.Items {
+		items[i] = toPoolJSON(p)
+	}
+	respondJSON(c, http.StatusOK, gin.H{
+		"items":  items,
+		"total":  page.Total,
+		"offset": page.Offset,
+		"limit":  page.Limit,
+	})
+}
+
+// ---------------------------------------------------------------------------
+// POST /pools
+// ---------------------------------------------------------------------------
+
+func (h *PoolHandler) Create(c *gin.Context) {
+	var body struct {
+		Name     string  `json:"name"      binding:"required"`
+		Notes    *string `json:"notes"`
+		IsPublic *bool   `json:"is_public"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	created, err := h.poolSvc.Create(c.Request.Context(), service.PoolParams{
+		Name:     body.Name,
+		Notes:    body.Notes,
+		IsPublic: body.IsPublic,
+	})
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	respondJSON(c, http.StatusCreated, toPoolJSON(*created))
+}
+
+// ---------------------------------------------------------------------------
+// GET /pools/:pool_id
+// ---------------------------------------------------------------------------
+
+func (h *PoolHandler) Get(c *gin.Context) {
+	id, ok := parsePoolID(c)
+	if !ok {
+		return
+	}
+
+	p, err := h.poolSvc.Get(c.Request.Context(), id)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	respondJSON(c, http.StatusOK, toPoolJSON(*p))
+}
+
+// ---------------------------------------------------------------------------
+// POST /pools/:pool_id/views
+// ---------------------------------------------------------------------------
+
+// RecordView logs that the current user viewed the pool (activity.pool_views).
+func (h *PoolHandler) RecordView(c *gin.Context) {
+	id, ok := parsePoolID(c)
+	if !ok {
+		return
+	}
+
+	if err := h.poolSvc.RecordView(c.Request.Context(), id); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	c.Status(http.StatusNoContent)
+}
+
+// ---------------------------------------------------------------------------
+// PATCH /pools/:pool_id
+// ---------------------------------------------------------------------------
+
+func (h *PoolHandler) Update(c *gin.Context) {
+	id, ok := parsePoolID(c)
+	if !ok {
+		return
+	}
+
+	var raw map[string]any
+	if err := c.ShouldBindJSON(&raw); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	params := service.PoolParams{}
+	if v, ok := raw["name"]; ok {
+		if s, ok := v.(string); ok {
+			params.Name = s
+		}
+	}
+	if _, ok := raw["notes"]; ok {
+		if raw["notes"] == nil {
+			empty := ""
+			params.Notes = &empty
+		} else if s, ok := raw["notes"].(string); ok {
+			params.Notes = &s
+		}
+	}
+	if v, ok := raw["is_public"]; ok {
+		if b, ok := v.(bool); ok {
+			params.IsPublic = &b
+		}
+	}
+
+	updated, err := h.poolSvc.Update(c.Request.Context(), id, params)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	respondJSON(c, http.StatusOK, toPoolJSON(*updated))
+}
+
+// ---------------------------------------------------------------------------
+// DELETE /pools/:pool_id
+// ---------------------------------------------------------------------------
+
+func (h *PoolHandler) Delete(c *gin.Context) {
+	id, ok := parsePoolID(c)
+	if !ok {
+		return
+	}
+
+	if err := h.poolSvc.Delete(c.Request.Context(), id); err != nil {
+		respondError(c, err)
+		return
+	}
+	c.Status(http.StatusNoContent)
+}
+
+// ---------------------------------------------------------------------------
+// GET /pools/:pool_id/files
+// ---------------------------------------------------------------------------
+
+func (h *PoolHandler) ListFiles(c *gin.Context) {
+	poolID, ok := parsePoolID(c)
+	if !ok {
+		return
+	}
+
+	params := parsePoolFileParams(c)
+
+	page, err := h.poolSvc.ListFiles(c.Request.Context(), poolID, params)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	items := make([]poolFileJSON, len(page.Items))
+	for i, pf := range page.Items {
+		items[i] = toPoolFileJSON(pf)
+	}
+	respondJSON(c, http.StatusOK, gin.H{
+		"items":       items,
+		"next_cursor": page.NextCursor,
+	})
+}
+
+// ---------------------------------------------------------------------------
+// POST /pools/:pool_id/files
+// ---------------------------------------------------------------------------
+
+func (h *PoolHandler) AddFiles(c *gin.Context) {
+	poolID, ok := parsePoolID(c)
+	if !ok {
+		return
+	}
+
+	var body struct {
+		FileIDs  []string `json:"file_ids" binding:"required"`
+		Position *int     `json:"position"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	fileIDs := make([]uuid.UUID, 0, len(body.FileIDs))
+	for _, s := range body.FileIDs {
+		id, err := uuid.Parse(s)
+		if err != nil {
+			respondError(c, domain.ErrValidation)
+			return
+		}
+		fileIDs = append(fileIDs, id)
+	}
+
+	if err := h.poolSvc.AddFiles(c.Request.Context(), poolID, fileIDs, body.Position); err != nil {
+		respondError(c, err)
+		return
+	}
+	c.Status(http.StatusCreated)
+}
+
+// ---------------------------------------------------------------------------
+// POST /pools/:pool_id/files/remove
+// ---------------------------------------------------------------------------
+
+func (h *PoolHandler) RemoveFiles(c *gin.Context) {
+	poolID, ok := parsePoolID(c)
+	if !ok {
+		return
+	}
+
+	var body struct {
+		FileIDs []string `json:"file_ids" binding:"required"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	fileIDs := make([]uuid.UUID, 0, len(body.FileIDs))
+	for _, s := range body.FileIDs {
+		id, err := uuid.Parse(s)
+		if err != nil {
+			respondError(c, domain.ErrValidation)
+			return
+		}
+		fileIDs = append(fileIDs, id)
+	}
+
+	if err := h.poolSvc.RemoveFiles(c.Request.Context(), poolID, fileIDs); err != nil {
+		respondError(c, err)
+		return
+	}
+	c.Status(http.StatusNoContent)
+}
+
+// ---------------------------------------------------------------------------
+// PUT /pools/:pool_id/files/reorder
+// ---------------------------------------------------------------------------
+
+func (h *PoolHandler) Reorder(c *gin.Context) {
+	poolID, ok := parsePoolID(c)
+	if !ok {
+		return
+	}
+
+	var body struct {
+		FileIDs []string `json:"file_ids" binding:"required"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	fileIDs := make([]uuid.UUID, 0, len(body.FileIDs))
+	for _, s := range body.FileIDs {
+		id, err := uuid.Parse(s)
+		if err != nil {
+			respondError(c, domain.ErrValidation)
+			return
+		}
+		fileIDs = append(fileIDs, id)
+	}
+
+	if err := h.poolSvc.Reorder(c.Request.Context(), poolID, fileIDs); err != nil {
+		respondError(c, err)
+		return
+	}
+	c.Status(http.StatusNoContent)
+}

backend/internal/handler/ratelimit.go

@@ -0,0 +1,77 @@
+package handler
+
+import (
+	"net/http"
+	"sync"
+	"time"
+
+	"github.com/gin-gonic/gin"
+)
+
+// rateLimiter is a process-local, fixed-window per-key request limiter used to
+// throttle unauthenticated endpoints (login, refresh) against brute force. It
+// is best-effort: counts live in memory and reset on restart.
+type rateLimiter struct {
+	mu     sync.Mutex
+	counts map[string]*rateWindow
+	limit  int
+	window time.Duration
+}
+
+type rateWindow struct {
+	count int
+	reset time.Time
+}
+
+// newRateLimiter allows up to limit requests per key within each window.
+func newRateLimiter(limit int, window time.Duration) *rateLimiter {
+	return &rateLimiter{
+		counts: make(map[string]*rateWindow),
+		limit:  limit,
+		window: window,
+	}
+}
+
+// allow records a request for key and reports whether it is within the limit.
+func (rl *rateLimiter) allow(key string) bool {
+	now := time.Now()
+
+	rl.mu.Lock()
+	defer rl.mu.Unlock()
+
+	// Opportunistically prune expired entries so the map cannot grow without
+	// bound under a flood of distinct client IPs.
+	if len(rl.counts) > 10000 {
+		for k, w := range rl.counts {
+			if now.After(w.reset) {
+				delete(rl.counts, k)
+			}
+		}
+	}
+
+	w, ok := rl.counts[key]
+	if !ok || now.After(w.reset) {
+		rl.counts[key] = &rateWindow{count: 1, reset: now.Add(rl.window)}
+		return true
+	}
+	if w.count >= rl.limit {
+		return false
+	}
+	w.count++
+	return true
+}
+
+// Middleware throttles requests by client IP, returning 429 when over the limit.
+func (rl *rateLimiter) Middleware() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		if !rl.allow(c.ClientIP()) {
+			c.JSON(http.StatusTooManyRequests, errorBody{
+				Code:    "rate_limited",
+				Message: "too many requests, please try again later",
+			})
+			c.Abort()
+			return
+		}
+		c.Next()
+	}
+}

backend/internal/handler/response.go

@@ -0,0 +1,55 @@
+package handler
+
+import (
+	"errors"
+	"net/http"
+
+	"github.com/gin-gonic/gin"
+
+	"tanabata/backend/internal/domain"
+)
+
+// errorBody is the JSON shape returned for all error responses.
+type errorBody struct {
+	Code    string `json:"code"`
+	Message string `json:"message"`
+}
+
+func respondJSON(c *gin.Context, status int, data any) {
+	c.JSON(status, data)
+}
+
+// respondError maps a domain error to the appropriate HTTP status and writes
+// a JSON error body. Unknown errors become 500.
+func respondError(c *gin.Context, err error) {
+	var de *domain.DomainError
+	if errors.As(err, &de) {
+		c.JSON(domainStatus(de), errorBody{Code: de.Code(), Message: de.Error()})
+		return
+	}
+	c.JSON(http.StatusInternalServerError, errorBody{
+		Code:    "internal_error",
+		Message: "internal server error",
+	})
+}
+
+// domainStatus maps a DomainError sentinel to its HTTP status code per the
+// error mapping table in docs/GO_PROJECT_STRUCTURE.md.
+func domainStatus(de *domain.DomainError) int {
+	switch de {
+	case domain.ErrNotFound:
+		return http.StatusNotFound
+	case domain.ErrForbidden:
+		return http.StatusForbidden
+	case domain.ErrUnauthorized:
+		return http.StatusUnauthorized
+	case domain.ErrConflict:
+		return http.StatusConflict
+	case domain.ErrValidation:
+		return http.StatusBadRequest
+	case domain.ErrUnsupportedMIME:
+		return http.StatusUnsupportedMediaType
+	default:
+		return http.StatusInternalServerError
+	}
+}

backend/internal/handler/router.go

@@ -0,0 +1,193 @@
+package handler
+
+import (
+	"net/http"
+	"time"
+
+	"github.com/gin-gonic/gin"
+)
+
+// securityHeaders sets conservative response headers on every response: prevent
+// MIME sniffing of served file content, forbid framing, and suppress the
+// Referer header on outbound navigations.
+func securityHeaders() gin.HandlerFunc {
+	return func(c *gin.Context) {
+		h := c.Writer.Header()
+		h.Set("X-Content-Type-Options", "nosniff")
+		h.Set("X-Frame-Options", "DENY")
+		h.Set("Referrer-Policy", "no-referrer")
+		c.Next()
+	}
+}
+
+// NewRouter builds and returns a configured Gin engine.
+func NewRouter(
+	auth *AuthMiddleware,
+	authHandler *AuthHandler,
+	fileHandler *FileHandler,
+	tagHandler *TagHandler,
+	categoryHandler *CategoryHandler,
+	poolHandler *PoolHandler,
+	userHandler *UserHandler,
+	aclHandler *ACLHandler,
+	auditHandler *AuditHandler,
+	staticDir string,
+) *gin.Engine {
+	r := gin.New()
+	r.Use(gin.Logger(), gin.Recovery(), securityHeaders())
+
+	// Health check — no auth required.
+	r.GET("/health", func(c *gin.Context) {
+		c.JSON(http.StatusOK, gin.H{"status": "ok"})
+	})
+
+	v1 := r.Group("/api/v1")
+
+	// -------------------------------------------------------------------------
+	// Auth
+	// -------------------------------------------------------------------------
+	authGroup := v1.Group("/auth")
+	{
+		// Throttle credential endpoints per client IP to slow brute force.
+		authLimiter := newRateLimiter(10, time.Minute).Middleware()
+		authGroup.POST("/login", authLimiter, authHandler.Login)
+		authGroup.POST("/refresh", authLimiter, authHandler.Refresh)
+
+		protected := authGroup.Group("", auth.Handle())
+		{
+			protected.POST("/logout", authHandler.Logout)
+			protected.GET("/sessions", authHandler.ListSessions)
+			protected.DELETE("/sessions/:id", authHandler.TerminateSession)
+		}
+	}
+
+	// -------------------------------------------------------------------------
+	// Files (all require auth)
+	// -------------------------------------------------------------------------
+	files := v1.Group("/files", auth.Handle())
+	{
+		files.GET("", fileHandler.List)
+		files.POST("", fileHandler.Upload)
+
+		// Bulk + import routes registered before /:id to prevent param collision.
+		files.POST("/bulk/tags", fileHandler.BulkSetTags)
+		files.POST("/bulk/delete", fileHandler.BulkDelete)
+		files.POST("/bulk/common-tags", fileHandler.CommonTags)
+		files.POST("/import", fileHandler.Import)
+
+		// Per-file routes.
+		files.GET("/:id", fileHandler.GetMeta)
+		files.PATCH("/:id", fileHandler.UpdateMeta)
+		files.DELETE("/:id", fileHandler.SoftDelete)
+
+		files.GET("/:id/content", fileHandler.GetContent)
+		files.PUT("/:id/content", fileHandler.ReplaceContent)
+		files.GET("/:id/thumbnail", fileHandler.GetThumbnail)
+		files.GET("/:id/preview", fileHandler.GetPreview)
+		files.POST("/:id/views", fileHandler.RecordView)
+		files.POST("/:id/restore", fileHandler.Restore)
+		files.DELETE("/:id/permanent", fileHandler.PermanentDelete)
+
+		// File–tag relations — served by TagHandler for auto-rule support.
+		files.GET("/:id/tags", tagHandler.FileListTags)
+		files.PUT("/:id/tags", tagHandler.FileSetTags)
+		files.PUT("/:id/tags/:tag_id", tagHandler.FileAddTag)
+		files.DELETE("/:id/tags/:tag_id", tagHandler.FileRemoveTag)
+	}
+
+	// -------------------------------------------------------------------------
+	// Tags (all require auth)
+	// -------------------------------------------------------------------------
+	tags := v1.Group("/tags", auth.Handle())
+	{
+		tags.GET("", tagHandler.List)
+		tags.POST("", tagHandler.Create)
+
+		tags.GET("/:tag_id", tagHandler.Get)
+		tags.PATCH("/:tag_id", tagHandler.Update)
+		tags.DELETE("/:tag_id", tagHandler.Delete)
+
+		tags.GET("/:tag_id/files", tagHandler.ListFiles)
+
+		tags.GET("/:tag_id/rules", tagHandler.ListRules)
+		tags.POST("/:tag_id/rules", tagHandler.CreateRule)
+		tags.PATCH("/:tag_id/rules/:then_tag_id", tagHandler.PatchRule)
+		tags.DELETE("/:tag_id/rules/:then_tag_id", tagHandler.DeleteRule)
+	}
+
+	// -------------------------------------------------------------------------
+	// Categories (all require auth)
+	// -------------------------------------------------------------------------
+	categories := v1.Group("/categories", auth.Handle())
+	{
+		categories.GET("", categoryHandler.List)
+		categories.POST("", categoryHandler.Create)
+
+		categories.GET("/:category_id", categoryHandler.Get)
+		categories.PATCH("/:category_id", categoryHandler.Update)
+		categories.DELETE("/:category_id", categoryHandler.Delete)
+
+		categories.GET("/:category_id/tags", categoryHandler.ListTags)
+	}
+
+	// -------------------------------------------------------------------------
+	// Pools (all require auth)
+	// -------------------------------------------------------------------------
+	pools := v1.Group("/pools", auth.Handle())
+	{
+		pools.GET("", poolHandler.List)
+		pools.POST("", poolHandler.Create)
+
+		pools.GET("/:pool_id", poolHandler.Get)
+		pools.PATCH("/:pool_id", poolHandler.Update)
+		pools.DELETE("/:pool_id", poolHandler.Delete)
+		pools.POST("/:pool_id/views", poolHandler.RecordView)
+
+		// Sub-routes registered before /:pool_id/files to avoid param conflicts.
+		pools.POST("/:pool_id/files/remove", poolHandler.RemoveFiles)
+		pools.PUT("/:pool_id/files/reorder", poolHandler.Reorder)
+
+		pools.GET("/:pool_id/files", poolHandler.ListFiles)
+		pools.POST("/:pool_id/files", poolHandler.AddFiles)
+	}
+
+	// -------------------------------------------------------------------------
+	// Users (auth required; admin checks enforced in handler)
+	// -------------------------------------------------------------------------
+	users := v1.Group("/users", auth.Handle())
+	{
+		// /users/me must be registered before /:user_id to avoid param capture.
+		users.GET("/me", userHandler.GetMe)
+		users.PATCH("/me", userHandler.UpdateMe)
+
+		users.GET("", userHandler.List)
+		users.POST("", userHandler.Create)
+
+		users.GET("/:user_id", userHandler.Get)
+		users.PATCH("/:user_id", userHandler.UpdateAdmin)
+		users.DELETE("/:user_id", userHandler.Delete)
+	}
+
+	// -------------------------------------------------------------------------
+	// ACL (auth required)
+	// -------------------------------------------------------------------------
+	acl := v1.Group("/acl", auth.Handle())
+	{
+		acl.GET("/:object_type/:object_id", aclHandler.GetPermissions)
+		acl.PUT("/:object_type/:object_id", aclHandler.SetPermissions)
+	}
+
+	// -------------------------------------------------------------------------
+	// Audit (auth required; admin check enforced in handler)
+	// -------------------------------------------------------------------------
+	v1.GET("/audit", auth.Handle(), auditHandler.List)
+
+	// Serve the built single-page app on the same port as the API. When
+	// staticDir is empty (local development) the Vite dev server serves the UI
+	// instead, so the API runs standalone and unknown routes 404 normally.
+	if staticDir != "" {
+		r.NoRoute(spaHandler(staticDir))
+	}
+
+	return r
+}

backend/internal/handler/static.go

@@ -0,0 +1,74 @@
+package handler
+
+import (
+	"mime"
+	"net/http"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+)
+
+func init() {
+	// Go's mime table doesn't know .webmanifest; register it so the PWA manifest
+	// is served as JSON and isn't rejected by the X-Content-Type-Options header.
+	_ = mime.AddExtensionType(".webmanifest", "application/manifest+json")
+}
+
+// spaHandler serves the built single-page app from dir. It is wired as the
+// router's NoRoute handler, so it only sees requests that matched no API route.
+//
+// A request whose path maps to a real file on disk is served directly (with
+// cache headers tuned to SvelteKit's adapter-static output). Anything else
+// falls back to index.html so the client-side router can resolve deep links
+// like /pools/123. Unknown /api/ paths return a JSON 404 instead of the HTML
+// shell, keeping API error responses machine-readable.
+func spaHandler(dir string) gin.HandlerFunc {
+	indexPath := filepath.Join(dir, "index.html")
+
+	return func(c *gin.Context) {
+		reqPath := c.Request.URL.Path
+
+		if strings.HasPrefix(reqPath, "/api/") {
+			c.JSON(http.StatusNotFound, errorBody{
+				Code:    "not_found",
+				Message: "resource not found",
+			})
+			return
+		}
+
+		// Resolve the request to a path inside dir. Cleaning an absolute path
+		// collapses any "../" segments before the join, so the result can never
+		// escape dir — this is the traversal guard.
+		clean := path.Clean("/" + reqPath)
+		target := filepath.Join(dir, filepath.FromSlash(clean))
+
+		if info, err := os.Stat(target); err == nil && !info.IsDir() {
+			c.Header("Cache-Control", cacheControl(clean))
+			c.File(target)
+			return
+		}
+
+		// SPA fallback: serve the shell, never cached so a new deploy is picked
+		// up immediately on the next navigation.
+		c.Header("Cache-Control", "no-cache")
+		c.File(indexPath)
+	}
+}
+
+// cacheControl returns the Cache-Control value for a served static asset.
+// SvelteKit emits content-hashed files under /_app/immutable — those are safe
+// to cache forever. The service worker must never be cached, or clients pin to
+// a stale shell. Everything else gets a short, revalidated TTL.
+func cacheControl(p string) string {
+	switch {
+	case strings.HasPrefix(p, "/_app/immutable/"):
+		return "public, max-age=31536000, immutable"
+	case p == "/service-worker.js":
+		return "no-cache"
+	default:
+		return "public, max-age=3600"
+	}
+}

backend/internal/handler/tag_handler.go

@@ -0,0 +1,552 @@
+package handler
+
+import (
+	"net/http"
+	"strconv"
+
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+	"tanabata/backend/internal/service"
+)
+
+// TagHandler handles all /tags endpoints.
+type TagHandler struct {
+	tagSvc  *service.TagService
+	fileSvc *service.FileService
+}
+
+// NewTagHandler creates a TagHandler.
+func NewTagHandler(tagSvc *service.TagService, fileSvc *service.FileService) *TagHandler {
+	return &TagHandler{tagSvc: tagSvc, fileSvc: fileSvc}
+}
+
+// ---------------------------------------------------------------------------
+// Response types
+// ---------------------------------------------------------------------------
+
+type tagRuleJSON struct {
+	WhenTagID   string `json:"when_tag_id"`
+	ThenTagID   string `json:"then_tag_id"`
+	ThenTagName string `json:"then_tag_name"`
+	IsActive    bool   `json:"is_active"`
+}
+
+func toTagRuleJSON(r domain.TagRule) tagRuleJSON {
+	return tagRuleJSON{
+		WhenTagID:   r.WhenTagID.String(),
+		ThenTagID:   r.ThenTagID.String(),
+		ThenTagName: r.ThenTagName,
+		IsActive:    r.IsActive,
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+func parseTagID(c *gin.Context) (uuid.UUID, bool) {
+	id, err := uuid.Parse(c.Param("tag_id"))
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return uuid.UUID{}, false
+	}
+	return id, true
+}
+
+func parseOffsetParams(c *gin.Context, defaultSort string) port.OffsetParams {
+	limit := 50
+	if s := c.Query("limit"); s != "" {
+		if n, err := strconv.Atoi(s); err == nil && n > 0 && n <= 200 {
+			limit = n
+		}
+	}
+	offset := 0
+	if s := c.Query("offset"); s != "" {
+		if n, err := strconv.Atoi(s); err == nil && n >= 0 {
+			offset = n
+		}
+	}
+	sort := c.DefaultQuery("sort", defaultSort)
+	order := c.DefaultQuery("order", "desc")
+	search := c.Query("search")
+	return port.OffsetParams{Sort: sort, Order: order, Search: search, Limit: limit, Offset: offset}
+}
+
+// ---------------------------------------------------------------------------
+// GET /tags
+// ---------------------------------------------------------------------------
+
+func (h *TagHandler) List(c *gin.Context) {
+	params := parseOffsetParams(c, "created")
+
+	page, err := h.tagSvc.List(c.Request.Context(), params)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	items := make([]tagJSON, len(page.Items))
+	for i, t := range page.Items {
+		items[i] = toTagJSON(t)
+	}
+	respondJSON(c, http.StatusOK, gin.H{
+		"items":  items,
+		"total":  page.Total,
+		"offset": page.Offset,
+		"limit":  page.Limit,
+	})
+}
+
+// ---------------------------------------------------------------------------
+// POST /tags
+// ---------------------------------------------------------------------------
+
+func (h *TagHandler) Create(c *gin.Context) {
+	var body struct {
+		Name       string  `json:"name"       binding:"required"`
+		Notes      *string `json:"notes"`
+		Color      *string `json:"color"`
+		CategoryID *string `json:"category_id"`
+		IsPublic   *bool   `json:"is_public"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	params := service.TagParams{
+		Name:     body.Name,
+		Notes:    body.Notes,
+		Color:    body.Color,
+		IsPublic: body.IsPublic,
+	}
+	if body.CategoryID != nil {
+		id, err := uuid.Parse(*body.CategoryID)
+		if err != nil {
+			respondError(c, domain.ErrValidation)
+			return
+		}
+		params.CategoryID = &id
+	}
+
+	t, err := h.tagSvc.Create(c.Request.Context(), params)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	respondJSON(c, http.StatusCreated, toTagJSON(*t))
+}
+
+// ---------------------------------------------------------------------------
+// GET /tags/:tag_id
+// ---------------------------------------------------------------------------
+
+func (h *TagHandler) Get(c *gin.Context) {
+	id, ok := parseTagID(c)
+	if !ok {
+		return
+	}
+
+	t, err := h.tagSvc.Get(c.Request.Context(), id)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	respondJSON(c, http.StatusOK, toTagJSON(*t))
+}
+
+// ---------------------------------------------------------------------------
+// PATCH /tags/:tag_id
+// ---------------------------------------------------------------------------
+
+func (h *TagHandler) Update(c *gin.Context) {
+	id, ok := parseTagID(c)
+	if !ok {
+		return
+	}
+
+	// Use a raw map to distinguish "field absent" from "field = null".
+	var raw map[string]any
+	if err := c.ShouldBindJSON(&raw); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	params := service.TagParams{}
+
+	if v, ok := raw["name"]; ok {
+		if s, ok := v.(string); ok {
+			params.Name = s
+		}
+	}
+	if _, ok := raw["notes"]; ok {
+		if raw["notes"] == nil {
+			params.Notes = ptr("")
+		} else if s, ok := raw["notes"].(string); ok {
+			params.Notes = &s
+		}
+	}
+	if _, ok := raw["color"]; ok {
+		if raw["color"] == nil {
+			nilStr := ""
+			params.Color = &nilStr
+		} else if s, ok := raw["color"].(string); ok {
+			params.Color = &s
+		}
+	}
+	if _, ok := raw["category_id"]; ok {
+		if raw["category_id"] == nil {
+			nilID := uuid.Nil
+			params.CategoryID = &nilID // signals "unassign"
+		} else if s, ok := raw["category_id"].(string); ok {
+			cid, err := uuid.Parse(s)
+			if err != nil {
+				respondError(c, domain.ErrValidation)
+				return
+			}
+			params.CategoryID = &cid
+		}
+	}
+	if v, ok := raw["is_public"]; ok {
+		if b, ok := v.(bool); ok {
+			params.IsPublic = &b
+		}
+	}
+
+	t, err := h.tagSvc.Update(c.Request.Context(), id, params)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	respondJSON(c, http.StatusOK, toTagJSON(*t))
+}
+
+// ---------------------------------------------------------------------------
+// DELETE /tags/:tag_id
+// ---------------------------------------------------------------------------
+
+func (h *TagHandler) Delete(c *gin.Context) {
+	id, ok := parseTagID(c)
+	if !ok {
+		return
+	}
+
+	if err := h.tagSvc.Delete(c.Request.Context(), id); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	c.Status(http.StatusNoContent)
+}
+
+// ---------------------------------------------------------------------------
+// GET /tags/:tag_id/files
+// ---------------------------------------------------------------------------
+
+func (h *TagHandler) ListFiles(c *gin.Context) {
+	id, ok := parseTagID(c)
+	if !ok {
+		return
+	}
+
+	limit := 50
+	if s := c.Query("limit"); s != "" {
+		if n, err := strconv.Atoi(s); err == nil && n > 0 && n <= 200 {
+			limit = n
+		}
+	}
+
+	// Delegate to file service with a tag filter.
+	page, err := h.fileSvc.List(c.Request.Context(), domain.FileListParams{
+		Cursor:    c.Query("cursor"),
+		Direction: "forward",
+		Limit:     limit,
+		Sort:      "created",
+		Order:     "desc",
+		Filter:    "{t=" + id.String() + "}",
+	})
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	items := make([]fileJSON, len(page.Items))
+	for i, f := range page.Items {
+		items[i] = toFileJSON(f)
+	}
+	respondJSON(c, http.StatusOK, gin.H{
+		"items":       items,
+		"next_cursor": page.NextCursor,
+		"prev_cursor": page.PrevCursor,
+	})
+}
+
+// ---------------------------------------------------------------------------
+// GET /tags/:tag_id/rules
+// ---------------------------------------------------------------------------
+
+func (h *TagHandler) ListRules(c *gin.Context) {
+	id, ok := parseTagID(c)
+	if !ok {
+		return
+	}
+
+	rules, err := h.tagSvc.ListRules(c.Request.Context(), id)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	items := make([]tagRuleJSON, len(rules))
+	for i, r := range rules {
+		items[i] = toTagRuleJSON(r)
+	}
+	respondJSON(c, http.StatusOK, items)
+}
+
+// ---------------------------------------------------------------------------
+// POST /tags/:tag_id/rules
+// ---------------------------------------------------------------------------
+
+func (h *TagHandler) CreateRule(c *gin.Context) {
+	whenTagID, ok := parseTagID(c)
+	if !ok {
+		return
+	}
+
+	var body struct {
+		ThenTagID       string `json:"then_tag_id" binding:"required"`
+		IsActive        *bool  `json:"is_active"`
+		ApplyToExisting *bool  `json:"apply_to_existing"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	thenTagID, err := uuid.Parse(body.ThenTagID)
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	isActive := true
+	if body.IsActive != nil {
+		isActive = *body.IsActive
+	}
+	applyToExisting := true
+	if body.ApplyToExisting != nil {
+		applyToExisting = *body.ApplyToExisting
+	}
+
+	rule, err := h.tagSvc.CreateRule(c.Request.Context(), whenTagID, thenTagID, isActive, applyToExisting)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	respondJSON(c, http.StatusCreated, toTagRuleJSON(*rule))
+}
+
+// ---------------------------------------------------------------------------
+// PATCH /tags/:tag_id/rules/:then_tag_id
+// ---------------------------------------------------------------------------
+
+func (h *TagHandler) PatchRule(c *gin.Context) {
+	whenTagID, ok := parseTagID(c)
+	if !ok {
+		return
+	}
+
+	thenTagID, err := uuid.Parse(c.Param("then_tag_id"))
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	var body struct {
+		IsActive        *bool `json:"is_active"`
+		ApplyToExisting *bool `json:"apply_to_existing"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil || body.IsActive == nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	applyToExisting := false
+	if body.ApplyToExisting != nil {
+		applyToExisting = *body.ApplyToExisting
+	}
+
+	rule, err := h.tagSvc.SetRuleActive(c.Request.Context(), whenTagID, thenTagID, *body.IsActive, applyToExisting)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	respondJSON(c, http.StatusOK, toTagRuleJSON(*rule))
+}
+
+// ---------------------------------------------------------------------------
+// DELETE /tags/:tag_id/rules/:then_tag_id
+// ---------------------------------------------------------------------------
+
+func (h *TagHandler) DeleteRule(c *gin.Context) {
+	whenTagID, ok := parseTagID(c)
+	if !ok {
+		return
+	}
+
+	thenTagID, err := uuid.Parse(c.Param("then_tag_id"))
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	if err := h.tagSvc.DeleteRule(c.Request.Context(), whenTagID, thenTagID); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	c.Status(http.StatusNoContent)
+}
+
+// ---------------------------------------------------------------------------
+// File-tag endpoints wired through TagService
+// (called from file routes, shared handler logic lives here)
+// ---------------------------------------------------------------------------
+
+// FileListTags handles GET /files/:id/tags.
+func (h *TagHandler) FileListTags(c *gin.Context) {
+	fileID, err := uuid.Parse(c.Param("id"))
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	if err := h.fileSvc.AuthorizeView(c.Request.Context(), fileID); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	tags, err := h.tagSvc.ListFileTags(c.Request.Context(), fileID)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	items := make([]tagJSON, len(tags))
+	for i, t := range tags {
+		items[i] = toTagJSON(t)
+	}
+	respondJSON(c, http.StatusOK, items)
+}
+
+// FileSetTags handles PUT /files/:id/tags.
+func (h *TagHandler) FileSetTags(c *gin.Context) {
+	fileID, err := uuid.Parse(c.Param("id"))
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	var body struct {
+		TagIDs []string `json:"tag_ids" binding:"required"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	tagIDs, err := parseUUIDs(body.TagIDs)
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	if err := h.fileSvc.AuthorizeEdit(c.Request.Context(), fileID); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	tags, err := h.tagSvc.SetFileTags(c.Request.Context(), fileID, tagIDs)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	items := make([]tagJSON, len(tags))
+	for i, t := range tags {
+		items[i] = toTagJSON(t)
+	}
+	respondJSON(c, http.StatusOK, items)
+}
+
+// FileAddTag handles PUT /files/:id/tags/:tag_id.
+func (h *TagHandler) FileAddTag(c *gin.Context) {
+	fileID, err := uuid.Parse(c.Param("id"))
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+	tagID, err := uuid.Parse(c.Param("tag_id"))
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	if err := h.fileSvc.AuthorizeEdit(c.Request.Context(), fileID); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	tags, err := h.tagSvc.AddFileTag(c.Request.Context(), fileID, tagID)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	items := make([]tagJSON, len(tags))
+	for i, t := range tags {
+		items[i] = toTagJSON(t)
+	}
+	respondJSON(c, http.StatusOK, items)
+}
+
+// FileRemoveTag handles DELETE /files/:id/tags/:tag_id.
+func (h *TagHandler) FileRemoveTag(c *gin.Context) {
+	fileID, err := uuid.Parse(c.Param("id"))
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+	tagID, err := uuid.Parse(c.Param("tag_id"))
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	if err := h.fileSvc.AuthorizeEdit(c.Request.Context(), fileID); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	if err := h.tagSvc.RemoveFileTag(c.Request.Context(), fileID, tagID); err != nil {
+		respondError(c, err)
+		return
+	}
+
+	c.Status(http.StatusNoContent)
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+func ptr(s string) *string { return &s }

backend/internal/handler/user_handler.go

@@ -0,0 +1,258 @@
+package handler
+
+import (
+	"net/http"
+	"strconv"
+
+	"github.com/gin-gonic/gin"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+	"tanabata/backend/internal/service"
+)
+
+// UserHandler handles all /users endpoints.
+type UserHandler struct {
+	userSvc *service.UserService
+}
+
+// NewUserHandler creates a UserHandler.
+func NewUserHandler(userSvc *service.UserService) *UserHandler {
+	return &UserHandler{userSvc: userSvc}
+}
+
+// ---------------------------------------------------------------------------
+// Response types
+// ---------------------------------------------------------------------------
+
+type userJSON struct {
+	ID        int16  `json:"id"`
+	Name      string `json:"name"`
+	IsAdmin   bool   `json:"is_admin"`
+	CanCreate bool   `json:"can_create"`
+	IsBlocked bool   `json:"is_blocked"`
+}
+
+func toUserJSON(u domain.User) userJSON {
+	return userJSON{
+		ID:        u.ID,
+		Name:      u.Name,
+		IsAdmin:   u.IsAdmin,
+		CanCreate: u.CanCreate,
+		IsBlocked: u.IsBlocked,
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Helpers
+// ---------------------------------------------------------------------------
+
+func requireAdmin(c *gin.Context) bool {
+	_, isAdmin, _ := domain.UserFromContext(c.Request.Context())
+	if !isAdmin {
+		respondError(c, domain.ErrForbidden)
+		return false
+	}
+	return true
+}
+
+func parseUserID(c *gin.Context) (int16, bool) {
+	n, err := strconv.ParseInt(c.Param("user_id"), 10, 16)
+	if err != nil {
+		respondError(c, domain.ErrValidation)
+		return 0, false
+	}
+	return int16(n), true
+}
+
+// ---------------------------------------------------------------------------
+// GET /users/me
+// ---------------------------------------------------------------------------
+
+func (h *UserHandler) GetMe(c *gin.Context) {
+	u, err := h.userSvc.GetMe(c.Request.Context())
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	respondJSON(c, http.StatusOK, toUserJSON(*u))
+}
+
+// ---------------------------------------------------------------------------
+// PATCH /users/me
+// ---------------------------------------------------------------------------
+
+func (h *UserHandler) UpdateMe(c *gin.Context) {
+	var body struct {
+		Name     string  `json:"name"`
+		Password *string `json:"password"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	updated, err := h.userSvc.UpdateMe(c.Request.Context(), service.UpdateMeParams{
+		Name:     body.Name,
+		Password: body.Password,
+	})
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	respondJSON(c, http.StatusOK, toUserJSON(*updated))
+}
+
+// ---------------------------------------------------------------------------
+// GET /users  (admin)
+// ---------------------------------------------------------------------------
+
+func (h *UserHandler) List(c *gin.Context) {
+	if !requireAdmin(c) {
+		return
+	}
+
+	params := port.OffsetParams{
+		Sort:  c.DefaultQuery("sort", "id"),
+		Order: c.DefaultQuery("order", "asc"),
+	}
+	if s := c.Query("limit"); s != "" {
+		if n, err := strconv.Atoi(s); err == nil {
+			params.Limit = n
+		}
+	}
+	if s := c.Query("offset"); s != "" {
+		if n, err := strconv.Atoi(s); err == nil {
+			params.Offset = n
+		}
+	}
+
+	page, err := h.userSvc.List(c.Request.Context(), params)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+
+	items := make([]userJSON, len(page.Items))
+	for i, u := range page.Items {
+		items[i] = toUserJSON(u)
+	}
+	respondJSON(c, http.StatusOK, gin.H{
+		"items":  items,
+		"total":  page.Total,
+		"offset": page.Offset,
+		"limit":  page.Limit,
+	})
+}
+
+// ---------------------------------------------------------------------------
+// POST /users  (admin)
+// ---------------------------------------------------------------------------
+
+func (h *UserHandler) Create(c *gin.Context) {
+	if !requireAdmin(c) {
+		return
+	}
+
+	var body struct {
+		Name      string `json:"name"     binding:"required"`
+		Password  string `json:"password" binding:"required"`
+		IsAdmin   bool   `json:"is_admin"`
+		CanCreate bool   `json:"can_create"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	created, err := h.userSvc.Create(c.Request.Context(), service.CreateUserParams{
+		Name:      body.Name,
+		Password:  body.Password,
+		IsAdmin:   body.IsAdmin,
+		CanCreate: body.CanCreate,
+	})
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	respondJSON(c, http.StatusCreated, toUserJSON(*created))
+}
+
+// ---------------------------------------------------------------------------
+// GET /users/:user_id  (admin)
+// ---------------------------------------------------------------------------
+
+func (h *UserHandler) Get(c *gin.Context) {
+	if !requireAdmin(c) {
+		return
+	}
+
+	id, ok := parseUserID(c)
+	if !ok {
+		return
+	}
+
+	u, err := h.userSvc.Get(c.Request.Context(), id)
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	respondJSON(c, http.StatusOK, toUserJSON(*u))
+}
+
+// ---------------------------------------------------------------------------
+// PATCH /users/:user_id  (admin)
+// ---------------------------------------------------------------------------
+
+func (h *UserHandler) UpdateAdmin(c *gin.Context) {
+	if !requireAdmin(c) {
+		return
+	}
+
+	id, ok := parseUserID(c)
+	if !ok {
+		return
+	}
+
+	var body struct {
+		IsAdmin   *bool `json:"is_admin"`
+		CanCreate *bool `json:"can_create"`
+		IsBlocked *bool `json:"is_blocked"`
+	}
+	if err := c.ShouldBindJSON(&body); err != nil {
+		respondError(c, domain.ErrValidation)
+		return
+	}
+
+	updated, err := h.userSvc.UpdateAdmin(c.Request.Context(), id, service.UpdateAdminParams{
+		IsAdmin:   body.IsAdmin,
+		CanCreate: body.CanCreate,
+		IsBlocked: body.IsBlocked,
+	})
+	if err != nil {
+		respondError(c, err)
+		return
+	}
+	respondJSON(c, http.StatusOK, toUserJSON(*updated))
+}
+
+// ---------------------------------------------------------------------------
+// DELETE /users/:user_id  (admin)
+// ---------------------------------------------------------------------------
+
+func (h *UserHandler) Delete(c *gin.Context) {
+	if !requireAdmin(c) {
+		return
+	}
+
+	id, ok := parseUserID(c)
+	if !ok {
+		return
+	}
+
+	if err := h.userSvc.Delete(c.Request.Context(), id); err != nil {
+		respondError(c, err)
+		return
+	}
+	c.Status(http.StatusNoContent)
+}

backend/internal/port/repository.go

@@ -0,0 +1,190 @@
+package port
+
+import (
+	"context"
+	"time"
+
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+)
+
+// Transactor executes fn inside a single database transaction.
+// All repository calls made within fn receive the transaction via context.
+type Transactor interface {
+	WithTx(ctx context.Context, fn func(ctx context.Context) error) error
+}
+
+// OffsetParams holds common offset-pagination and sort parameters.
+type OffsetParams struct {
+	Sort   string
+	Order  string // "asc" | "desc"
+	Search string
+	Offset int
+	Limit  int
+
+	// Visibility — populated by the service from the request context. When
+	// ViewerIsAdmin is false the repository restricts results to rows the viewer
+	// may see (public, owned, or explicitly granted). Ignored by user listing,
+	// which is admin-only.
+	ViewerID      int16
+	ViewerIsAdmin bool
+}
+
+// PoolFileListParams holds parameters for listing files inside a pool.
+type PoolFileListParams struct {
+	Cursor string
+	Limit  int
+	Filter string // filter DSL expression
+}
+
+// FileRepo is the persistence interface for file records.
+type FileRepo interface {
+	// List returns a cursor-based page of files.
+	List(ctx context.Context, params domain.FileListParams) (*domain.FilePage, error)
+	// GetByID returns the file with its tags loaded.
+	GetByID(ctx context.Context, id uuid.UUID) (*domain.File, error)
+	// Create inserts a new file record and returns it.
+	Create(ctx context.Context, f *domain.File) (*domain.File, error)
+	// Update applies partial metadata changes and returns the updated record.
+	Update(ctx context.Context, id uuid.UUID, f *domain.File) (*domain.File, error)
+	// SoftDelete moves a file to trash (sets is_deleted = true).
+	SoftDelete(ctx context.Context, id uuid.UUID) error
+	// Restore moves a file out of trash (sets is_deleted = false).
+	Restore(ctx context.Context, id uuid.UUID) (*domain.File, error)
+	// DeletePermanent removes a file record. Only allowed when is_deleted = true.
+	DeletePermanent(ctx context.Context, id uuid.UUID) error
+
+	// ListTags returns all tags assigned to a file.
+	ListTags(ctx context.Context, fileID uuid.UUID) ([]domain.Tag, error)
+	// SetTags replaces all tags on a file (full replace semantics).
+	SetTags(ctx context.Context, fileID uuid.UUID, tagIDs []uuid.UUID) error
+
+	// RecordView appends a view-history row (activity.file_views) for the user.
+	RecordView(ctx context.Context, fileID uuid.UUID, userID int16) error
+	// RecordTagUses logs the tags referenced in a filter DSL to
+	// activity.tag_uses, flagging each included or excluded. Best-effort
+	// analytics — callers may ignore the error.
+	RecordTagUses(ctx context.Context, userID int16, filterDSL string) error
+}
+
+// TagRepo is the persistence interface for tags.
+type TagRepo interface {
+	List(ctx context.Context, params OffsetParams) (*domain.TagOffsetPage, error)
+	// ListByCategory returns tags belonging to a specific category.
+	ListByCategory(ctx context.Context, categoryID uuid.UUID, params OffsetParams) (*domain.TagOffsetPage, error)
+	GetByID(ctx context.Context, id uuid.UUID) (*domain.Tag, error)
+	Create(ctx context.Context, t *domain.Tag) (*domain.Tag, error)
+	Update(ctx context.Context, id uuid.UUID, t *domain.Tag) (*domain.Tag, error)
+	Delete(ctx context.Context, id uuid.UUID) error
+
+	// ListByFile returns all tags assigned to a specific file, ordered by name.
+	ListByFile(ctx context.Context, fileID uuid.UUID) ([]domain.Tag, error)
+	// AddFileTag inserts a single file→tag relation. No-op if already present.
+	AddFileTag(ctx context.Context, fileID, tagID uuid.UUID) error
+	// RemoveFileTag deletes a single file→tag relation.
+	RemoveFileTag(ctx context.Context, fileID, tagID uuid.UUID) error
+	// SetFileTags replaces all tags on a file (full replace semantics).
+	SetFileTags(ctx context.Context, fileID uuid.UUID, tagIDs []uuid.UUID) error
+	// CommonTagsForFiles returns tags present on every one of the given files.
+	CommonTagsForFiles(ctx context.Context, fileIDs []uuid.UUID) ([]domain.Tag, error)
+	// PartialTagsForFiles returns tags present on some but not all of the given files.
+	PartialTagsForFiles(ctx context.Context, fileIDs []uuid.UUID) ([]domain.Tag, error)
+}
+
+// TagRuleRepo is the persistence interface for auto-tag rules.
+type TagRuleRepo interface {
+	// ListByTag returns all rules where WhenTagID == tagID.
+	ListByTag(ctx context.Context, tagID uuid.UUID) ([]domain.TagRule, error)
+	Create(ctx context.Context, r domain.TagRule) (*domain.TagRule, error)
+	// SetActive toggles a rule's is_active flag. When active and applyToExisting
+	// are both true, the full transitive expansion of thenTagID is retroactively
+	// applied to all files that already carry whenTagID.
+	SetActive(ctx context.Context, whenTagID, thenTagID uuid.UUID, active, applyToExisting bool) error
+	Delete(ctx context.Context, whenTagID, thenTagID uuid.UUID) error
+}
+
+// CategoryRepo is the persistence interface for categories.
+type CategoryRepo interface {
+	List(ctx context.Context, params OffsetParams) (*domain.CategoryOffsetPage, error)
+	GetByID(ctx context.Context, id uuid.UUID) (*domain.Category, error)
+	Create(ctx context.Context, c *domain.Category) (*domain.Category, error)
+	Update(ctx context.Context, id uuid.UUID, c *domain.Category) (*domain.Category, error)
+	Delete(ctx context.Context, id uuid.UUID) error
+}
+
+// PoolRepo is the persistence interface for pools and pool–file membership.
+type PoolRepo interface {
+	List(ctx context.Context, params OffsetParams) (*domain.PoolOffsetPage, error)
+	GetByID(ctx context.Context, id uuid.UUID) (*domain.Pool, error)
+	Create(ctx context.Context, p *domain.Pool) (*domain.Pool, error)
+	Update(ctx context.Context, id uuid.UUID, p *domain.Pool) (*domain.Pool, error)
+	Delete(ctx context.Context, id uuid.UUID) error
+
+	// ListFiles returns pool files ordered by position (cursor-based).
+	ListFiles(ctx context.Context, poolID uuid.UUID, params PoolFileListParams) (*domain.PoolFilePage, error)
+	// AddFiles appends files starting at position; nil position means append at end.
+	AddFiles(ctx context.Context, poolID uuid.UUID, fileIDs []uuid.UUID, position *int) error
+	// RemoveFiles removes files from the pool.
+	RemoveFiles(ctx context.Context, poolID uuid.UUID, fileIDs []uuid.UUID) error
+	// Reorder sets the full ordered sequence of file IDs in the pool.
+	Reorder(ctx context.Context, poolID uuid.UUID, fileIDs []uuid.UUID) error
+
+	// RecordView appends a view-history row (activity.pool_views) for the user.
+	RecordView(ctx context.Context, poolID uuid.UUID, userID int16) error
+}
+
+// UserRepo is the persistence interface for users.
+type UserRepo interface {
+	List(ctx context.Context, params OffsetParams) (*domain.UserPage, error)
+	GetByID(ctx context.Context, id int16) (*domain.User, error)
+	// GetByName is used during login to look up credentials.
+	GetByName(ctx context.Context, name string) (*domain.User, error)
+	Create(ctx context.Context, u *domain.User) (*domain.User, error)
+	Update(ctx context.Context, id int16, u *domain.User) (*domain.User, error)
+	Delete(ctx context.Context, id int16) error
+}
+
+// SessionRepo is the persistence interface for auth sessions.
+type SessionRepo interface {
+	// ListByUser returns all active sessions for a user.
+	ListByUser(ctx context.Context, userID int16) (*domain.SessionList, error)
+	// GetByID returns an active session by its ID, or ErrNotFound if it does not
+	// exist or has been deactivated.
+	GetByID(ctx context.Context, id int) (*domain.Session, error)
+	// GetByTokenHash looks up a session by the hashed refresh token.
+	GetByTokenHash(ctx context.Context, hash string) (*domain.Session, error)
+	Create(ctx context.Context, s *domain.Session) (*domain.Session, error)
+	// UpdateLastActivity refreshes the last_activity timestamp.
+	UpdateLastActivity(ctx context.Context, id int, t time.Time) error
+	// Delete terminates a single session.
+	Delete(ctx context.Context, id int) error
+	// DeleteByUserID terminates all sessions for a user (logout everywhere).
+	DeleteByUserID(ctx context.Context, userID int16) error
+}
+
+// ACLRepo is the persistence interface for per-object permissions.
+type ACLRepo interface {
+	// List returns all permission entries for a given object.
+	List(ctx context.Context, objectTypeID int16, objectID uuid.UUID) ([]domain.Permission, error)
+	// Get returns the permission entry for a specific user and object; returns
+	// ErrNotFound if no entry exists.
+	Get(ctx context.Context, userID int16, objectTypeID int16, objectID uuid.UUID) (*domain.Permission, error)
+	// Set replaces all permissions for an object (full replace semantics).
+	Set(ctx context.Context, objectTypeID int16, objectID uuid.UUID, perms []domain.Permission) error
+}
+
+// AuditRepo is the persistence interface for the audit log.
+type AuditRepo interface {
+	Log(ctx context.Context, entry domain.AuditEntry) error
+	List(ctx context.Context, filter domain.AuditFilter) (*domain.AuditPage, error)
+}
+
+// MimeRepo is the persistence interface for the MIME type whitelist.
+type MimeRepo interface {
+	// List returns all supported MIME types.
+	List(ctx context.Context) ([]domain.MIMEType, error)
+	// GetByName returns the MIME type record for a given MIME name (e.g. "image/jpeg").
+	// Returns ErrUnsupportedMIME if not in the whitelist.
+	GetByName(ctx context.Context, name string) (*domain.MIMEType, error)
+}

backend/internal/port/storage.go

@@ -0,0 +1,35 @@
+package port
+
+import (
+	"context"
+	"io"
+
+	"github.com/google/uuid"
+)
+
+// FileStorage abstracts disk (or object-store) operations for file content,
+// thumbnails, and previews.
+type FileStorage interface {
+	// Save writes the reader's content to storage and returns the number of
+	// bytes written.
+	Save(ctx context.Context, id uuid.UUID, r io.Reader) (int64, error)
+
+	// Read opens the file content for reading. The caller must close the returned
+	// ReadCloser.
+	Read(ctx context.Context, id uuid.UUID) (io.ReadCloser, error)
+
+	// Delete removes the file content from storage.
+	Delete(ctx context.Context, id uuid.UUID) error
+
+	// InvalidateCache removes any cached thumbnail/preview for the file so they
+	// are regenerated from the current content on next request.
+	InvalidateCache(ctx context.Context, id uuid.UUID) error
+
+	// Thumbnail opens the pre-generated thumbnail (JPEG). Returns ErrNotFound
+	// if the thumbnail has not been generated yet.
+	Thumbnail(ctx context.Context, id uuid.UUID) (io.ReadCloser, error)
+
+	// Preview opens the pre-generated preview image (JPEG). Returns ErrNotFound
+	// if the preview has not been generated yet.
+	Preview(ctx context.Context, id uuid.UUID) (io.ReadCloser, error)
+}

backend/internal/service/acl_service.go

@@ -0,0 +1,176 @@
+package service
+
+import (
+	"context"
+	"errors"
+
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+// ACLService handles access control checks and permission management.
+type ACLService struct {
+	aclRepo    port.ACLRepo
+	files      port.FileRepo
+	tags       port.TagRepo
+	categories port.CategoryRepo
+	pools      port.PoolRepo
+	tx         port.Transactor
+}
+
+// NewACLService creates an ACLService. The object repositories are used to
+// resolve an object's owner when authorizing permission management.
+func NewACLService(
+	aclRepo port.ACLRepo,
+	files port.FileRepo,
+	tags port.TagRepo,
+	categories port.CategoryRepo,
+	pools port.PoolRepo,
+	tx port.Transactor,
+) *ACLService {
+	return &ACLService{
+		aclRepo:    aclRepo,
+		files:      files,
+		tags:       tags,
+		categories: categories,
+		pools:      pools,
+		tx:         tx,
+	}
+}
+
+// CanView returns true if the user may view the object.
+// isAdmin, creatorID, isPublic must be populated from the object record by the caller.
+func (s *ACLService) CanView(
+	ctx context.Context,
+	userID int16, isAdmin bool,
+	creatorID int16, isPublic bool,
+	objectTypeID int16, objectID uuid.UUID,
+) (bool, error) {
+	if isAdmin {
+		return true, nil
+	}
+	if isPublic {
+		return true, nil
+	}
+	if userID == creatorID {
+		return true, nil
+	}
+	perm, err := s.aclRepo.Get(ctx, userID, objectTypeID, objectID)
+	if err != nil {
+		if errors.Is(err, domain.ErrNotFound) {
+			return false, nil
+		}
+		return false, err
+	}
+	return perm.CanView, nil
+}
+
+// CanEdit returns true if the user may edit the object.
+// is_public does not grant edit access; only admins, creators, and explicit grants.
+func (s *ACLService) CanEdit(
+	ctx context.Context,
+	userID int16, isAdmin bool,
+	creatorID int16,
+	objectTypeID int16, objectID uuid.UUID,
+) (bool, error) {
+	if isAdmin {
+		return true, nil
+	}
+	if userID == creatorID {
+		return true, nil
+	}
+	perm, err := s.aclRepo.Get(ctx, userID, objectTypeID, objectID)
+	if err != nil {
+		if errors.Is(err, domain.ErrNotFound) {
+			return false, nil
+		}
+		return false, err
+	}
+	return perm.CanEdit, nil
+}
+
+// GetPermissions returns all explicit ACL entries for an object. Only the
+// object's owner or an admin may inspect its permission list.
+func (s *ACLService) GetPermissions(
+	ctx context.Context,
+	userID int16, isAdmin bool,
+	objectTypeID int16, objectID uuid.UUID,
+) ([]domain.Permission, error) {
+	if err := s.authorizeManage(ctx, userID, isAdmin, objectTypeID, objectID); err != nil {
+		return nil, err
+	}
+	return s.aclRepo.List(ctx, objectTypeID, objectID)
+}
+
+// SetPermissions replaces all ACL entries for an object (full replace semantics).
+// Only the object's owner or an admin may change its permissions. The replace is
+// performed atomically inside a single transaction.
+func (s *ACLService) SetPermissions(
+	ctx context.Context,
+	userID int16, isAdmin bool,
+	objectTypeID int16, objectID uuid.UUID,
+	perms []domain.Permission,
+) error {
+	if err := s.authorizeManage(ctx, userID, isAdmin, objectTypeID, objectID); err != nil {
+		return err
+	}
+	return s.tx.WithTx(ctx, func(ctx context.Context) error {
+		return s.aclRepo.Set(ctx, objectTypeID, objectID, perms)
+	})
+}
+
+// authorizeManage returns nil if the user may manage the object's ACL
+// (admin or owner), ErrForbidden otherwise, or a propagated lookup error
+// (including ErrNotFound when the object does not exist).
+func (s *ACLService) authorizeManage(
+	ctx context.Context,
+	userID int16, isAdmin bool,
+	objectTypeID int16, objectID uuid.UUID,
+) error {
+	if isAdmin {
+		return nil
+	}
+	owner, err := s.objectOwner(ctx, objectTypeID, objectID)
+	if err != nil {
+		return err
+	}
+	if owner != userID {
+		return domain.ErrForbidden
+	}
+	return nil
+}
+
+// objectOwner resolves the creator ID of the object identified by
+// (objectTypeID, objectID). Returns ErrNotFound if the object does not exist.
+func (s *ACLService) objectOwner(ctx context.Context, objectTypeID int16, objectID uuid.UUID) (int16, error) {
+	switch objectTypeID {
+	case fileObjectTypeID:
+		obj, err := s.files.GetByID(ctx, objectID)
+		if err != nil {
+			return 0, err
+		}
+		return obj.CreatorID, nil
+	case tagObjectTypeID:
+		obj, err := s.tags.GetByID(ctx, objectID)
+		if err != nil {
+			return 0, err
+		}
+		return obj.CreatorID, nil
+	case categoryObjectTypeID:
+		obj, err := s.categories.GetByID(ctx, objectID)
+		if err != nil {
+			return 0, err
+		}
+		return obj.CreatorID, nil
+	case poolObjectTypeID:
+		obj, err := s.pools.GetByID(ctx, objectID)
+		if err != nil {
+			return 0, err
+		}
+		return obj.CreatorID, nil
+	default:
+		return 0, domain.ErrValidation
+	}
+}

backend/internal/service/audit_service.go

@@ -0,0 +1,57 @@
+package service
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+// AuditService records user actions to the audit trail.
+type AuditService struct {
+	repo port.AuditRepo
+}
+
+func NewAuditService(repo port.AuditRepo) *AuditService {
+	return &AuditService{repo: repo}
+}
+
+// Log records an action performed by the user in ctx.
+// objectType and objectID are optional — pass nil when the action has no target object.
+// details can be any JSON-serializable value, or nil.
+func (s *AuditService) Log(
+	ctx context.Context,
+	action string,
+	objectType *string,
+	objectID *uuid.UUID,
+	details any,
+) error {
+	userID, _, _ := domain.UserFromContext(ctx)
+
+	var raw json.RawMessage
+	if details != nil {
+		b, err := json.Marshal(details)
+		if err != nil {
+			return fmt.Errorf("AuditService.Log marshal details: %w", err)
+		}
+		raw = b
+	}
+
+	entry := domain.AuditEntry{
+		UserID:     userID,
+		Action:     action,
+		ObjectType: objectType,
+		ObjectID:   objectID,
+		Details:    raw,
+	}
+	return s.repo.Log(ctx, entry)
+}
+
+// Query returns a filtered, paginated page of audit log entries.
+func (s *AuditService) Query(ctx context.Context, filter domain.AuditFilter) (*domain.AuditPage, error) {
+	return s.repo.List(ctx, filter)
+}

backend/internal/service/auth_service.go

@@ -0,0 +1,295 @@
+package service
+
+import (
+	"context"
+	"crypto/rand"
+	"crypto/sha256"
+	"encoding/hex"
+	"fmt"
+	"time"
+
+	"github.com/golang-jwt/jwt/v5"
+	"golang.org/x/crypto/bcrypt"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+// Token types distinguish short-lived access tokens from long-lived refresh
+// tokens so the two cannot be substituted for one another.
+const (
+	tokenTypeAccess  = "access"
+	tokenTypeRefresh = "refresh"
+)
+
+// dummyPasswordHash is a valid bcrypt hash used to equalise the cost of a login
+// attempt against a non-existent user, preventing username enumeration via
+// response timing. It is the hash of a random string no one knows.
+const dummyPasswordHash = "$2a$10$N9qo8uLOickgx2ZMRZoMyeIjZAgcfl7p92ldGxad68LJZdL17lhWy"
+
+// Claims is the JWT payload for both access and refresh tokens.
+type Claims struct {
+	jwt.RegisteredClaims
+	UserID    int16  `json:"uid"`
+	IsAdmin   bool   `json:"adm"`
+	SessionID int    `json:"sid"`
+	TokenType string `json:"typ"`
+}
+
+// TokenPair holds an issued access/refresh token pair with the access TTL.
+type TokenPair struct {
+	AccessToken  string
+	RefreshToken string
+	ExpiresIn    int // access token TTL in seconds
+}
+
+// AuthService handles authentication and session lifecycle.
+type AuthService struct {
+	users      port.UserRepo
+	sessions   port.SessionRepo
+	secret     []byte
+	accessTTL  time.Duration
+	refreshTTL time.Duration
+}
+
+// NewAuthService creates an AuthService.
+func NewAuthService(
+	users port.UserRepo,
+	sessions port.SessionRepo,
+	jwtSecret string,
+	accessTTL time.Duration,
+	refreshTTL time.Duration,
+) *AuthService {
+	return &AuthService{
+		users:      users,
+		sessions:   sessions,
+		secret:     []byte(jwtSecret),
+		accessTTL:  accessTTL,
+		refreshTTL: refreshTTL,
+	}
+}
+
+// Login validates credentials, creates a session, and returns a token pair.
+func (s *AuthService) Login(ctx context.Context, name, password, userAgent string) (*TokenPair, error) {
+	user, err := s.users.GetByName(ctx, name)
+	if err != nil {
+		// Compare against a dummy hash so a missing user costs the same as a
+		// wrong password, and return ErrUnauthorized either way to avoid
+		// username enumeration.
+		_ = bcrypt.CompareHashAndPassword([]byte(dummyPasswordHash), []byte(password))
+		return nil, domain.ErrUnauthorized
+	}
+
+	// Verify the password before disclosing anything about account state, so a
+	// caller cannot distinguish "blocked" from "wrong password".
+	if err := bcrypt.CompareHashAndPassword([]byte(user.Password), []byte(password)); err != nil {
+		return nil, domain.ErrUnauthorized
+	}
+
+	if user.IsBlocked {
+		return nil, domain.ErrForbidden
+	}
+
+	return s.issuePair(ctx, user, userAgent)
+}
+
+// Logout deactivates the session identified by sessionID.
+func (s *AuthService) Logout(ctx context.Context, sessionID int) error {
+	if err := s.sessions.Delete(ctx, sessionID); err != nil {
+		return fmt.Errorf("logout: %w", err)
+	}
+	return nil
+}
+
+// Refresh validates a refresh token, issues a new token pair, and deactivates
+// the old session.
+func (s *AuthService) Refresh(ctx context.Context, refreshToken, userAgent string) (*TokenPair, error) {
+	claims, err := s.parseToken(refreshToken)
+	if err != nil || claims.TokenType != tokenTypeRefresh {
+		return nil, domain.ErrUnauthorized
+	}
+
+	session, err := s.sessions.GetByTokenHash(ctx, hashToken(refreshToken))
+	if err != nil {
+		return nil, domain.ErrUnauthorized
+	}
+
+	if session.ExpiresAt != nil && time.Now().After(*session.ExpiresAt) {
+		_ = s.sessions.Delete(ctx, session.ID)
+		return nil, domain.ErrUnauthorized
+	}
+
+	// Rotate: deactivate old session.
+	if err := s.sessions.Delete(ctx, session.ID); err != nil {
+		return nil, fmt.Errorf("deactivate old session: %w", err)
+	}
+
+	user, err := s.users.GetByID(ctx, claims.UserID)
+	if err != nil {
+		return nil, domain.ErrUnauthorized
+	}
+
+	if user.IsBlocked {
+		return nil, domain.ErrForbidden
+	}
+
+	return s.issuePair(ctx, user, userAgent)
+}
+
+// issuePair creates a session and the access/refresh token pair for user.
+//
+// The refresh token is issued first and its hash is stored as the session's
+// identity; the refresh token is located on /refresh purely by that hash, so it
+// carries no session ID. The access token then embeds the real session ID so it
+// can be revoked on logout. Because the stored hash is the hash of the token
+// actually returned, /refresh works (unlike the previous re-issue approach).
+func (s *AuthService) issuePair(ctx context.Context, user *domain.User, userAgent string) (*TokenPair, error) {
+	var expiresAt *time.Time
+	if s.refreshTTL > 0 {
+		t := time.Now().Add(s.refreshTTL)
+		expiresAt = &t
+	}
+
+	refreshToken, err := s.issueToken(user.ID, user.IsAdmin, 0, s.refreshTTL, tokenTypeRefresh)
+	if err != nil {
+		return nil, fmt.Errorf("issue refresh token: %w", err)
+	}
+
+	session, err := s.sessions.Create(ctx, &domain.Session{
+		TokenHash: hashToken(refreshToken),
+		UserID:    user.ID,
+		UserAgent: userAgent,
+		ExpiresAt: expiresAt,
+	})
+	if err != nil {
+		return nil, fmt.Errorf("create session: %w", err)
+	}
+
+	accessToken, err := s.issueToken(user.ID, user.IsAdmin, session.ID, s.accessTTL, tokenTypeAccess)
+	if err != nil {
+		return nil, fmt.Errorf("issue access token: %w", err)
+	}
+
+	return &TokenPair{
+		AccessToken:  accessToken,
+		RefreshToken: refreshToken,
+		ExpiresIn:    int(s.accessTTL.Seconds()),
+	}, nil
+}
+
+// ListSessions returns all active sessions for the given user.
+func (s *AuthService) ListSessions(ctx context.Context, userID int16, currentSessionID int) (*domain.SessionList, error) {
+	list, err := s.sessions.ListByUser(ctx, userID)
+	if err != nil {
+		return nil, fmt.Errorf("list sessions: %w", err)
+	}
+	for i := range list.Items {
+		list.Items[i].IsCurrent = list.Items[i].ID == currentSessionID
+	}
+	return list, nil
+}
+
+// TerminateSession deactivates a specific session, enforcing ownership.
+func (s *AuthService) TerminateSession(ctx context.Context, callerID int16, isAdmin bool, sessionID int) error {
+	if !isAdmin {
+		list, err := s.sessions.ListByUser(ctx, callerID)
+		if err != nil {
+			return fmt.Errorf("terminate session: %w", err)
+		}
+		owned := false
+		for _, sess := range list.Items {
+			if sess.ID == sessionID {
+				owned = true
+				break
+			}
+		}
+		if !owned {
+			return domain.ErrForbidden
+		}
+	}
+
+	if err := s.sessions.Delete(ctx, sessionID); err != nil {
+		return fmt.Errorf("terminate session: %w", err)
+	}
+	return nil
+}
+
+// ValidateAccessToken parses and validates an access token, returning its
+// claims. A refresh token is rejected (wrong type), and the token's session
+// must still be active — so logout, session termination, an admin block, or a
+// refresh rotation revoke any outstanding access tokens immediately rather than
+// only at expiry.
+func (s *AuthService) ValidateAccessToken(ctx context.Context, tokenStr string) (*Claims, error) {
+	claims, err := s.parseToken(tokenStr)
+	if err != nil {
+		return nil, domain.ErrUnauthorized
+	}
+	if claims.TokenType != tokenTypeAccess {
+		return nil, domain.ErrUnauthorized
+	}
+	if _, err := s.sessions.GetByID(ctx, claims.SessionID); err != nil {
+		return nil, domain.ErrUnauthorized
+	}
+	return claims, nil
+}
+
+// issueToken signs a JWT with the given parameters. A random JWT ID guarantees
+// uniqueness even for tokens minted within the same second.
+func (s *AuthService) issueToken(userID int16, isAdmin bool, sessionID int, ttl time.Duration, tokenType string) (string, error) {
+	jti, err := randomJTI()
+	if err != nil {
+		return "", err
+	}
+	now := time.Now()
+	claims := Claims{
+		RegisteredClaims: jwt.RegisteredClaims{
+			ID:        jti,
+			IssuedAt:  jwt.NewNumericDate(now),
+			ExpiresAt: jwt.NewNumericDate(now.Add(ttl)),
+		},
+		UserID:    userID,
+		IsAdmin:   isAdmin,
+		SessionID: sessionID,
+		TokenType: tokenType,
+	}
+	token := jwt.NewWithClaims(jwt.SigningMethodHS256, claims)
+	signed, err := token.SignedString(s.secret)
+	if err != nil {
+		return "", fmt.Errorf("sign token: %w", err)
+	}
+	return signed, nil
+}
+
+// parseToken verifies the signature and parses claims from a token string.
+func (s *AuthService) parseToken(tokenStr string) (*Claims, error) {
+	token, err := jwt.ParseWithClaims(tokenStr, &Claims{}, func(t *jwt.Token) (any, error) {
+		if _, ok := t.Method.(*jwt.SigningMethodHMAC); !ok {
+			return nil, fmt.Errorf("unexpected signing method: %v", t.Header["alg"])
+		}
+		return s.secret, nil
+	})
+	if err != nil || !token.Valid {
+		return nil, domain.ErrUnauthorized
+	}
+	claims, ok := token.Claims.(*Claims)
+	if !ok {
+		return nil, domain.ErrUnauthorized
+	}
+	return claims, nil
+}
+
+// hashToken returns the SHA-256 hex digest of a token string.
+// The raw token is never stored; only the hash goes to the database.
+func hashToken(token string) string {
+	sum := sha256.Sum256([]byte(token))
+	return hex.EncodeToString(sum[:])
+}
+
+// randomJTI returns a 128-bit random hex string for use as a JWT ID.
+func randomJTI() (string, error) {
+	b := make([]byte, 16)
+	if _, err := rand.Read(b); err != nil {
+		return "", fmt.Errorf("generate jti: %w", err)
+	}
+	return hex.EncodeToString(b), nil
+}

backend/internal/service/category_service.go

@@ -0,0 +1,179 @@
+package service
+
+import (
+	"context"
+	"encoding/json"
+
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+const categoryObjectType = "category"
+const categoryObjectTypeID int16 = 3 // third row in 007_seed_data.sql object_types
+
+// CategoryParams holds the fields for creating or patching a category.
+type CategoryParams struct {
+	Name     string
+	Notes    *string
+	Color    *string // nil = no change; pointer to empty string = clear
+	Metadata json.RawMessage
+	IsPublic *bool
+}
+
+// CategoryService handles category CRUD with ACL enforcement and audit logging.
+type CategoryService struct {
+	categories port.CategoryRepo
+	tags       port.TagRepo
+	acl        *ACLService
+	audit      *AuditService
+}
+
+// NewCategoryService creates a CategoryService.
+func NewCategoryService(
+	categories port.CategoryRepo,
+	tags port.TagRepo,
+	acl *ACLService,
+	audit *AuditService,
+) *CategoryService {
+	return &CategoryService{
+		categories: categories,
+		tags:       tags,
+		acl:        acl,
+		audit:      audit,
+	}
+}
+
+// ---------------------------------------------------------------------------
+// CRUD
+// ---------------------------------------------------------------------------
+
+// List returns a paginated list of categories the caller may see.
+func (s *CategoryService) List(ctx context.Context, params port.OffsetParams) (*domain.CategoryOffsetPage, error) {
+	params.ViewerID, params.ViewerIsAdmin, _ = domain.UserFromContext(ctx)
+	return s.categories.List(ctx, params)
+}
+
+// Get returns a category by ID, enforcing view ACL.
+func (s *CategoryService) Get(ctx context.Context, id uuid.UUID) (*domain.Category, error) {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+	c, err := s.categories.GetByID(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	ok, err := s.acl.CanView(ctx, userID, isAdmin, c.CreatorID, c.IsPublic, categoryObjectTypeID, id)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		return nil, domain.ErrForbidden
+	}
+	return c, nil
+}
+
+// Create inserts a new category record.
+func (s *CategoryService) Create(ctx context.Context, p CategoryParams) (*domain.Category, error) {
+	userID, _, _ := domain.UserFromContext(ctx)
+
+	c := &domain.Category{
+		Name:      p.Name,
+		Notes:     p.Notes,
+		Color:     p.Color,
+		Metadata:  p.Metadata,
+		CreatorID: userID,
+	}
+	if p.IsPublic != nil {
+		c.IsPublic = *p.IsPublic
+	}
+
+	created, err := s.categories.Create(ctx, c)
+	if err != nil {
+		return nil, err
+	}
+
+	objType := categoryObjectType
+	_ = s.audit.Log(ctx, "category_create", &objType, &created.ID, nil)
+	return created, nil
+}
+
+// Update applies a partial patch to a category.
+func (s *CategoryService) Update(ctx context.Context, id uuid.UUID, p CategoryParams) (*domain.Category, error) {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+
+	current, err := s.categories.GetByID(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	ok, err := s.acl.CanEdit(ctx, userID, isAdmin, current.CreatorID, categoryObjectTypeID, id)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		return nil, domain.ErrForbidden
+	}
+
+	patch := *current
+	if p.Name != "" {
+		patch.Name = p.Name
+	}
+	if p.Notes != nil {
+		patch.Notes = p.Notes
+	}
+	if p.Color != nil {
+		patch.Color = p.Color
+	}
+	if len(p.Metadata) > 0 {
+		patch.Metadata = p.Metadata
+	}
+	if p.IsPublic != nil {
+		patch.IsPublic = *p.IsPublic
+	}
+
+	updated, err := s.categories.Update(ctx, id, &patch)
+	if err != nil {
+		return nil, err
+	}
+
+	objType := categoryObjectType
+	_ = s.audit.Log(ctx, "category_edit", &objType, &id, nil)
+	return updated, nil
+}
+
+// Delete removes a category by ID, enforcing edit ACL.
+func (s *CategoryService) Delete(ctx context.Context, id uuid.UUID) error {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+
+	c, err := s.categories.GetByID(ctx, id)
+	if err != nil {
+		return err
+	}
+
+	ok, err := s.acl.CanEdit(ctx, userID, isAdmin, c.CreatorID, categoryObjectTypeID, id)
+	if err != nil {
+		return err
+	}
+	if !ok {
+		return domain.ErrForbidden
+	}
+
+	if err := s.categories.Delete(ctx, id); err != nil {
+		return err
+	}
+
+	objType := categoryObjectType
+	_ = s.audit.Log(ctx, "category_delete", &objType, &id, nil)
+	return nil
+}
+
+// ---------------------------------------------------------------------------
+// Tags in category
+// ---------------------------------------------------------------------------
+
+// ListTags returns a paginated list of tags in this category that the caller
+// may see.
+func (s *CategoryService) ListTags(ctx context.Context, categoryID uuid.UUID, params port.OffsetParams) (*domain.TagOffsetPage, error) {
+	params.ViewerID, params.ViewerIsAdmin, _ = domain.UserFromContext(ctx)
+	return s.tags.ListByCategory(ctx, categoryID, params)
+}

backend/internal/service/file_service.go

@@ -0,0 +1,714 @@
+package service
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"fmt"
+	"io"
+	"os"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/gabriel-vasile/mimetype"
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+const fileObjectType = "file"
+
+// fileObjectTypeID is the primary key of the "file" row in core.object_types.
+// It matches the first value inserted in 007_seed_data.sql.
+const fileObjectTypeID int16 = 1
+
+// UploadParams holds the parameters for uploading a new file.
+type UploadParams struct {
+	Reader          io.Reader
+	MIMEType        string
+	OriginalName    *string
+	Notes           *string
+	Metadata        json.RawMessage
+	ContentDatetime *time.Time
+	// ContentDatetimeFallback is used for content_datetime only when neither an
+	// explicit ContentDatetime nor an EXIF date is available (e.g. the source
+	// file's mtime on a server-side import).
+	ContentDatetimeFallback *time.Time
+	IsPublic                bool
+	TagIDs                  []uuid.UUID
+}
+
+// UpdateParams holds the parameters for updating file metadata.
+type UpdateParams struct {
+	OriginalName    *string
+	Notes           *string
+	Metadata        json.RawMessage
+	ContentDatetime *time.Time
+	IsPublic        *bool
+	TagIDs          *[]uuid.UUID // nil means don't change tags
+}
+
+// ContentResult holds the open reader and metadata for a file download.
+type ContentResult struct {
+	Body         io.ReadCloser
+	MIMEType     string
+	OriginalName *string
+}
+
+// ImportFileError records a failed file during an import operation.
+type ImportFileError struct {
+	Filename string `json:"filename"`
+	Reason   string `json:"reason"`
+}
+
+// ImportResult summarises a directory import.
+type ImportResult struct {
+	Imported int               `json:"imported"`
+	Skipped  int               `json:"skipped"`
+	Errors   []ImportFileError `json:"errors"`
+}
+
+// ImportEvent is one progress message streamed during an import, letting the UI
+// show a live progress bar and a per-file status list. Type is the discriminator:
+//
+//	"start" — total is the number of entries about to be processed.
+//	"file"  — one entry finished: index (1-based), filename, status, optional reason.
+//	"done"  — final tallies (imported/skipped/errors).
+type ImportEvent struct {
+	Type     string `json:"type"`
+	Total    int    `json:"total,omitempty"`
+	Index    int    `json:"index,omitempty"`
+	Filename string `json:"filename,omitempty"`
+	Status   string `json:"status,omitempty"` // "imported" | "skipped" | "error"
+	Reason   string `json:"reason,omitempty"`
+	Imported int    `json:"imported,omitempty"`
+	Skipped  int    `json:"skipped,omitempty"`
+	Errors   int    `json:"errors,omitempty"`
+}
+
+// FileService handles business logic for file records.
+type FileService struct {
+	files      port.FileRepo
+	mimes      port.MimeRepo
+	storage    port.FileStorage
+	acl        *ACLService
+	audit      *AuditService
+	tags       *TagService
+	tx         port.Transactor
+	importPath string // default server-side import directory
+}
+
+// NewFileService creates a FileService.
+func NewFileService(
+	files port.FileRepo,
+	mimes port.MimeRepo,
+	storage port.FileStorage,
+	acl *ACLService,
+	audit *AuditService,
+	tags *TagService,
+	tx port.Transactor,
+	importPath string,
+) *FileService {
+	return &FileService{
+		files:      files,
+		mimes:      mimes,
+		storage:    storage,
+		acl:        acl,
+		audit:      audit,
+		tags:       tags,
+		tx:         tx,
+		importPath: importPath,
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Core CRUD
+// ---------------------------------------------------------------------------
+
+// Upload validates the MIME type, saves the file to storage, creates the DB
+// record, and applies any initial tags — all within a single transaction.
+// If ContentDatetime is nil and the metadata carries a capture date, it is used.
+func (s *FileService) Upload(ctx context.Context, p UploadParams) (*domain.File, error) {
+	userID, _, _ := domain.UserFromContext(ctx)
+
+	// Validate MIME type against the whitelist.
+	mime, err := s.mimes.GetByName(ctx, p.MIMEType)
+	if err != nil {
+		return nil, err // ErrUnsupportedMIME or DB error
+	}
+
+	// Buffer the upload so we can extract EXIF without re-reading storage.
+	var buf bytes.Buffer
+	if _, err := io.Copy(&buf, p.Reader); err != nil {
+		return nil, fmt.Errorf("FileService.Upload: read body: %w", err)
+	}
+	data := buf.Bytes()
+
+	// Extract rich metadata (best-effort; covers images, video and audio).
+	var origName string
+	if p.OriginalName != nil {
+		origName = *p.OriginalName
+	}
+	exifData, exifDatetime := extractMetadata(data, origName, p.ContentDatetimeFallback)
+
+	// Resolve content datetime: explicit > metadata date > fallback (e.g. import mtime) > zero.
+	var contentDatetime time.Time
+	if p.ContentDatetime != nil {
+		contentDatetime = *p.ContentDatetime
+	} else if exifDatetime != nil {
+		contentDatetime = *exifDatetime
+	} else if p.ContentDatetimeFallback != nil {
+		contentDatetime = *p.ContentDatetimeFallback
+	}
+
+	// Assign UUID v7 so CreatedAt can be derived from it later.
+	fileID, err := uuid.NewV7()
+	if err != nil {
+		return nil, fmt.Errorf("FileService.Upload: generate UUID: %w", err)
+	}
+
+	// Save file bytes to disk before opening the transaction so that a disk
+	// failure does not abort an otherwise healthy DB transaction.
+	if _, err := s.storage.Save(ctx, fileID, bytes.NewReader(data)); err != nil {
+		return nil, fmt.Errorf("FileService.Upload: save to storage: %w", err)
+	}
+
+	var created *domain.File
+	txErr := s.tx.WithTx(ctx, func(ctx context.Context) error {
+		f := &domain.File{
+			ID:              fileID,
+			OriginalName:    p.OriginalName,
+			MIMEType:        mime.Name,
+			MIMEExtension:   mime.Extension,
+			ContentDatetime: contentDatetime,
+			Notes:           p.Notes,
+			Metadata:        p.Metadata,
+			EXIF:            exifData,
+			CreatorID:       userID,
+			IsPublic:        p.IsPublic,
+		}
+
+		var createErr error
+		created, createErr = s.files.Create(ctx, f)
+		if createErr != nil {
+			return createErr
+		}
+
+		if len(p.TagIDs) > 0 {
+			tags, err := s.tags.SetFileTags(ctx, created.ID, p.TagIDs)
+			if err != nil {
+				return err
+			}
+			created.Tags = tags
+		}
+		return nil
+	})
+	if txErr != nil {
+		// Attempt to clean up the orphaned file; ignore cleanup errors.
+		_ = s.storage.Delete(ctx, fileID)
+		return nil, txErr
+	}
+
+	objType := fileObjectType
+	_ = s.audit.Log(ctx, "file_create", &objType, &created.ID, nil)
+	return created, nil
+}
+
+// Get returns a file by ID, enforcing view ACL.
+func (s *FileService) Get(ctx context.Context, id uuid.UUID) (*domain.File, error) {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+
+	f, err := s.files.GetByID(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	ok, err := s.acl.CanView(ctx, userID, isAdmin, f.CreatorID, f.IsPublic, fileObjectTypeID, id)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		return nil, domain.ErrForbidden
+	}
+	return f, nil
+}
+
+// RecordView appends a view-history entry for the current user, enforcing view
+// ACL (you can only record a view of a file you may see).
+func (s *FileService) RecordView(ctx context.Context, id uuid.UUID) error {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+
+	f, err := s.files.GetByID(ctx, id)
+	if err != nil {
+		return err
+	}
+
+	ok, err := s.acl.CanView(ctx, userID, isAdmin, f.CreatorID, f.IsPublic, fileObjectTypeID, id)
+	if err != nil {
+		return err
+	}
+	if !ok {
+		return domain.ErrForbidden
+	}
+	return s.files.RecordView(ctx, id, userID)
+}
+
+// Update applies metadata changes to a file, enforcing edit ACL.
+func (s *FileService) Update(ctx context.Context, id uuid.UUID, p UpdateParams) (*domain.File, error) {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+
+	f, err := s.files.GetByID(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	ok, err := s.acl.CanEdit(ctx, userID, isAdmin, f.CreatorID, fileObjectTypeID, id)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		return nil, domain.ErrForbidden
+	}
+
+	patch := &domain.File{}
+	if p.OriginalName != nil {
+		patch.OriginalName = p.OriginalName
+	}
+	if p.Notes != nil {
+		patch.Notes = p.Notes
+	}
+	if p.Metadata != nil {
+		patch.Metadata = p.Metadata
+	}
+	if p.ContentDatetime != nil {
+		patch.ContentDatetime = *p.ContentDatetime
+	}
+	if p.IsPublic != nil {
+		patch.IsPublic = *p.IsPublic
+	}
+
+	var updated *domain.File
+	txErr := s.tx.WithTx(ctx, func(ctx context.Context) error {
+		var updateErr error
+		updated, updateErr = s.files.Update(ctx, id, patch)
+		if updateErr != nil {
+			return updateErr
+		}
+		if p.TagIDs != nil {
+			tags, err := s.tags.SetFileTags(ctx, id, *p.TagIDs)
+			if err != nil {
+				return err
+			}
+			updated.Tags = tags
+		}
+		return nil
+	})
+	if txErr != nil {
+		return nil, txErr
+	}
+
+	objType := fileObjectType
+	_ = s.audit.Log(ctx, "file_edit", &objType, &id, nil)
+	return updated, nil
+}
+
+// Delete soft-deletes a file (moves to trash), enforcing edit ACL.
+func (s *FileService) Delete(ctx context.Context, id uuid.UUID) error {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+
+	f, err := s.files.GetByID(ctx, id)
+	if err != nil {
+		return err
+	}
+
+	ok, err := s.acl.CanEdit(ctx, userID, isAdmin, f.CreatorID, fileObjectTypeID, id)
+	if err != nil {
+		return err
+	}
+	if !ok {
+		return domain.ErrForbidden
+	}
+
+	if err := s.files.SoftDelete(ctx, id); err != nil {
+		return err
+	}
+
+	objType := fileObjectType
+	_ = s.audit.Log(ctx, "file_delete", &objType, &id, nil)
+	return nil
+}
+
+// Restore moves a soft-deleted file out of trash, enforcing edit ACL.
+func (s *FileService) Restore(ctx context.Context, id uuid.UUID) (*domain.File, error) {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+
+	f, err := s.files.GetByID(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	ok, err := s.acl.CanEdit(ctx, userID, isAdmin, f.CreatorID, fileObjectTypeID, id)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		return nil, domain.ErrForbidden
+	}
+
+	restored, err := s.files.Restore(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	objType := fileObjectType
+	_ = s.audit.Log(ctx, "file_restore", &objType, &id, nil)
+	return restored, nil
+}
+
+// PermanentDelete removes the file record and its stored bytes. Only allowed
+// when the file is already in trash.
+func (s *FileService) PermanentDelete(ctx context.Context, id uuid.UUID) error {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+
+	f, err := s.files.GetByID(ctx, id)
+	if err != nil {
+		return err
+	}
+	if !f.IsDeleted {
+		return domain.ErrConflict
+	}
+
+	ok, err := s.acl.CanEdit(ctx, userID, isAdmin, f.CreatorID, fileObjectTypeID, id)
+	if err != nil {
+		return err
+	}
+	if !ok {
+		return domain.ErrForbidden
+	}
+
+	if err := s.files.DeletePermanent(ctx, id); err != nil {
+		return err
+	}
+	_ = s.storage.Delete(ctx, id)
+	_ = s.storage.InvalidateCache(ctx, id)
+
+	objType := fileObjectType
+	_ = s.audit.Log(ctx, "file_permanent_delete", &objType, &id, nil)
+	return nil
+}
+
+// Replace swaps the stored bytes for a file with new content.
+func (s *FileService) Replace(ctx context.Context, id uuid.UUID, p UploadParams) (*domain.File, error) {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+
+	f, err := s.files.GetByID(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	ok, err := s.acl.CanEdit(ctx, userID, isAdmin, f.CreatorID, fileObjectTypeID, id)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		return nil, domain.ErrForbidden
+	}
+
+	mime, err := s.mimes.GetByName(ctx, p.MIMEType)
+	if err != nil {
+		return nil, err
+	}
+
+	var buf bytes.Buffer
+	if _, err := io.Copy(&buf, p.Reader); err != nil {
+		return nil, fmt.Errorf("FileService.Replace: read body: %w", err)
+	}
+	data := buf.Bytes()
+	var origName string
+	if p.OriginalName != nil {
+		origName = *p.OriginalName
+	}
+	exifData, _ := extractMetadata(data, origName, nil)
+
+	if _, err := s.storage.Save(ctx, id, bytes.NewReader(data)); err != nil {
+		return nil, fmt.Errorf("FileService.Replace: save to storage: %w", err)
+	}
+	// Drop stale thumbnail/preview so they regenerate from the new content.
+	_ = s.storage.InvalidateCache(ctx, id)
+
+	patch := &domain.File{
+		MIMEType:      mime.Name,
+		MIMEExtension: mime.Extension,
+		EXIF:          exifData,
+	}
+	if p.OriginalName != nil {
+		patch.OriginalName = p.OriginalName
+	}
+
+	updated, err := s.files.Update(ctx, id, patch)
+	if err != nil {
+		return nil, err
+	}
+
+	objType := fileObjectType
+	_ = s.audit.Log(ctx, "file_replace", &objType, &id, nil)
+	return updated, nil
+}
+
+// List delegates to FileRepo with the given params, restricting results to
+// files the caller may see (unless they are an admin).
+func (s *FileService) List(ctx context.Context, params domain.FileListParams) (*domain.FilePage, error) {
+	params.ViewerID, params.ViewerIsAdmin, _ = domain.UserFromContext(ctx)
+
+	page, err := s.files.List(ctx, params)
+	if err != nil {
+		return nil, err
+	}
+
+	// Log tag usage when a filter is first applied — not on pagination (cursor)
+	// or an anchored return, so a single browse counts once. Best-effort
+	// analytics; a failed write never breaks the listing.
+	if params.Filter != "" && params.Cursor == "" && params.Anchor == nil && params.ViewerID != 0 {
+		_ = s.files.RecordTagUses(ctx, params.ViewerID, params.Filter)
+	}
+
+	return page, nil
+}
+
+// AuthorizeView ensures the caller may view the file. Returns ErrNotFound if the
+// file does not exist or ErrForbidden if the caller lacks view access.
+func (s *FileService) AuthorizeView(ctx context.Context, id uuid.UUID) error {
+	_, err := s.Get(ctx, id)
+	return err
+}
+
+// AuthorizeEdit ensures the caller may edit the file. Returns ErrNotFound if the
+// file does not exist or ErrForbidden if the caller lacks edit access.
+func (s *FileService) AuthorizeEdit(ctx context.Context, id uuid.UUID) error {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+
+	f, err := s.files.GetByID(ctx, id)
+	if err != nil {
+		return err
+	}
+	ok, err := s.acl.CanEdit(ctx, userID, isAdmin, f.CreatorID, fileObjectTypeID, id)
+	if err != nil {
+		return err
+	}
+	if !ok {
+		return domain.ErrForbidden
+	}
+	return nil
+}
+
+// ---------------------------------------------------------------------------
+// Content / thumbnail / preview streaming
+// ---------------------------------------------------------------------------
+
+// GetContent opens the raw file for download, enforcing view ACL.
+func (s *FileService) GetContent(ctx context.Context, id uuid.UUID) (*ContentResult, error) {
+	f, err := s.Get(ctx, id) // ACL checked inside Get
+	if err != nil {
+		return nil, err
+	}
+	rc, err := s.storage.Read(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	return &ContentResult{
+		Body:         rc,
+		MIMEType:     f.MIMEType,
+		OriginalName: f.OriginalName,
+	}, nil
+}
+
+// GetThumbnail returns the thumbnail JPEG, enforcing view ACL.
+func (s *FileService) GetThumbnail(ctx context.Context, id uuid.UUID) (io.ReadCloser, error) {
+	if _, err := s.Get(ctx, id); err != nil {
+		return nil, err
+	}
+	return s.storage.Thumbnail(ctx, id)
+}
+
+// GetPreview returns the preview JPEG, enforcing view ACL.
+func (s *FileService) GetPreview(ctx context.Context, id uuid.UUID) (io.ReadCloser, error) {
+	if _, err := s.Get(ctx, id); err != nil {
+		return nil, err
+	}
+	return s.storage.Preview(ctx, id)
+}
+
+// ---------------------------------------------------------------------------
+// Bulk operations
+// ---------------------------------------------------------------------------
+
+// BulkDelete soft-deletes multiple files. Files the caller cannot edit are silently skipped.
+func (s *FileService) BulkDelete(ctx context.Context, fileIDs []uuid.UUID) error {
+	for _, id := range fileIDs {
+		if err := s.Delete(ctx, id); err != nil {
+			if err == domain.ErrNotFound || err == domain.ErrForbidden {
+				continue
+			}
+			return err
+		}
+	}
+	return nil
+}
+
+// ---------------------------------------------------------------------------
+// Import
+// ---------------------------------------------------------------------------
+
+// Import scans a server-side directory and uploads all supported files.
+// If path is empty, the configured default import path is used.
+//
+// onProgress, when non-nil, receives a "start" event, one "file" event per
+// directory entry as it is processed, and a final "done" event — letting a
+// caller stream live progress. It is always called from this goroutine (never
+// concurrently). The aggregate result is also returned for non-streaming callers.
+func (s *FileService) Import(ctx context.Context, path string, onProgress func(ImportEvent)) (*ImportResult, error) {
+	if s.importPath == "" {
+		return nil, domain.ErrValidation
+	}
+
+	dir := s.importPath
+	if path != "" {
+		// Confine caller-supplied paths to the configured import directory so a
+		// directory-traversal value cannot read arbitrary host files.
+		confined, err := confineToBase(s.importPath, path)
+		if err != nil {
+			return nil, err
+		}
+		dir = confined
+	}
+
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		return nil, fmt.Errorf("FileService.Import: read dir %q: %w", dir, err)
+	}
+
+	emit := func(ev ImportEvent) {
+		if onProgress != nil {
+			onProgress(ev)
+		}
+	}
+
+	result := &ImportResult{Errors: []ImportFileError{}}
+	total := len(entries)
+	emit(ImportEvent{Type: "start", Total: total})
+
+	for i, entry := range entries {
+		name := entry.Name()
+		file := func(status, reason string) {
+			emit(ImportEvent{
+				Type: "file", Index: i + 1, Total: total,
+				Filename: name, Status: status, Reason: reason,
+			})
+		}
+		fail := func(reason string) {
+			result.Errors = append(result.Errors, ImportFileError{Filename: name, Reason: reason})
+			file("error", reason)
+		}
+
+		if entry.IsDir() {
+			result.Skipped++
+			file("skipped", "directory")
+			continue
+		}
+
+		fullPath := filepath.Join(dir, name)
+
+		mt, err := mimetype.DetectFile(fullPath)
+		if err != nil {
+			fail(fmt.Sprintf("MIME detection failed: %s", err))
+			continue
+		}
+
+		mimeStr := mt.String()
+		// Strip parameters (e.g. "text/plain; charset=utf-8" → "text/plain").
+		if j := strings.IndexByte(mimeStr, ';'); j >= 0 {
+			mimeStr = mimeStr[:j]
+		}
+
+		if _, err := s.mimes.GetByName(ctx, mimeStr); err != nil {
+			result.Skipped++
+			file("skipped", "unsupported type: "+mimeStr)
+			continue
+		}
+
+		f, err := os.Open(fullPath)
+		if err != nil {
+			fail(fmt.Sprintf("open failed: %s", err))
+			continue
+		}
+
+		// Preserve the file's mtime as a content_datetime fallback (used only when
+		// the file has no EXIF date) — once the source is removed below it's the
+		// only date left for non-photo files.
+		var mtime *time.Time
+		if info, statErr := entry.Info(); statErr == nil {
+			t := info.ModTime()
+			mtime = &t
+		}
+
+		_, uploadErr := s.Upload(ctx, UploadParams{
+			Reader:                  f,
+			MIMEType:                mimeStr,
+			OriginalName:            &name,
+			ContentDatetimeFallback: mtime,
+		})
+		f.Close()
+
+		if uploadErr != nil {
+			fail(uploadErr.Error())
+			continue
+		}
+		result.Imported++
+
+		// Remove the source on success so the import folder drains and re-running
+		// doesn't duplicate. The file is already safely copied into storage; a
+		// removal failure is reported but doesn't undo the import.
+		if rmErr := os.Remove(fullPath); rmErr != nil {
+			reason := fmt.Sprintf("imported, but failed to remove source: %s", rmErr)
+			result.Errors = append(result.Errors, ImportFileError{Filename: name, Reason: reason})
+			file("imported", reason) // imported, with a warning
+			continue
+		}
+		file("imported", "")
+	}
+
+	emit(ImportEvent{
+		Type: "done", Total: total,
+		Imported: result.Imported, Skipped: result.Skipped, Errors: len(result.Errors),
+	})
+
+	return result, nil
+}
+
+// ---------------------------------------------------------------------------
+// Internal helpers
+// ---------------------------------------------------------------------------
+
+// confineToBase resolves target and verifies it does not escape base (after
+// cleaning and resolving "..") so a caller cannot read files outside the
+// configured import directory. Returns the cleaned absolute path on success.
+func confineToBase(base, target string) (string, error) {
+	absBase, err := filepath.Abs(base)
+	if err != nil {
+		return "", domain.ErrValidation
+	}
+	absTarget, err := filepath.Abs(target)
+	if err != nil {
+		return "", domain.ErrValidation
+	}
+	rel, err := filepath.Rel(absBase, absTarget)
+	if err != nil {
+		return "", domain.ErrValidation
+	}
+	if rel == ".." || strings.HasPrefix(rel, ".."+string(os.PathSeparator)) {
+		return "", domain.ErrForbidden
+	}
+	return absTarget, nil
+}

backend/internal/service/metadata.go

@@ -0,0 +1,183 @@
+package service
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"strings"
+	"time"
+
+	"github.com/rwcarlsen/goexif/exif"
+)
+
+// exiftoolPath is resolved once at startup. When exiftool isn't installed we
+// skip the subprocess and fall back to the pure-Go EXIF reader, so the server
+// still runs (with thinner metadata) on hosts without it.
+var exiftoolPath, _ = exec.LookPath("exiftool")
+
+// metadataTimeout bounds a single exiftool invocation so a pathological file
+// can't wedge an upload.
+const metadataTimeout = 30 * time.Second
+
+// metaTempFileKeys are exiftool fields that describe the temporary file we feed
+// it rather than the content. Dropping them avoids leaking internal paths and
+// recording the temp file's permissions/inode timestamps.
+var metaTempFileKeys = []string{
+	"SourceFile",
+	"Directory",
+	"FileAccessDate",
+	"FileInodeChangeDate",
+	"FilePermissions",
+}
+
+// metaDateKeys are the metadata fields, in priority order, holding the moment
+// the content was actually captured/created — photos first, then video atoms.
+var metaDateKeys = []string{
+	"DateTimeOriginal",
+	"CreateDate",
+	"MediaCreateDate",
+	"TrackCreateDate",
+	"ModifyDate",
+}
+
+// extractMetadata returns rich metadata as JSON plus the best content datetime
+// it can find. It prefers exiftool, which understands video, audio and every
+// image format and emits machine-readable numeric values (the basis for later
+// analytics); when exiftool is unavailable it falls back to the pure-Go EXIF
+// reader, which only handles JPEG/TIFF.
+//
+// originalName supplies the extension exiftool uses for format detection and the
+// FileName reported back. mtime, when set (e.g. a server-side import), is stamped
+// onto the temp file so FileModifyDate reflects the real source.
+func extractMetadata(data []byte, originalName string, mtime *time.Time) (json.RawMessage, *time.Time) {
+	if exiftoolPath != "" {
+		if raw, dt, ok := exiftoolExtract(data, originalName, mtime); ok {
+			return raw, dt
+		}
+	}
+	return extractEXIFWithDatetime(data)
+}
+
+// exiftoolExtract stages the bytes in a temp file and shells out to exiftool.
+// It returns ok=false on any failure so the caller can fall back.
+func exiftoolExtract(data []byte, originalName string, mtime *time.Time) (json.RawMessage, *time.Time, bool) {
+	// exiftool reads a real file far more reliably than a pipe (it seeks freely,
+	// e.g. to a trailing MP4 moov atom), so stage the bytes in a temp file whose
+	// extension matches the original for accurate format detection.
+	tmp, err := os.CreateTemp("", "tfm-meta-*"+filepath.Ext(originalName))
+	if err != nil {
+		return nil, nil, false
+	}
+	tmpName := tmp.Name()
+	defer os.Remove(tmpName)
+
+	if _, err := tmp.Write(data); err != nil {
+		tmp.Close()
+		return nil, nil, false
+	}
+	if err := tmp.Close(); err != nil {
+		return nil, nil, false
+	}
+	if mtime != nil {
+		_ = os.Chtimes(tmpName, *mtime, *mtime)
+	}
+
+	ctx, cancel := context.WithTimeout(context.Background(), metadataTimeout)
+	defer cancel()
+	// -n forces raw numeric/machine values for every tag (no "3.53 Mbps" strings)
+	// so the metadata is analytics-ready. -all extracts every tag. largefilesupport
+	// handles multi-GB videos. Output is a one-element JSON array.
+	out, err := exec.CommandContext(ctx, exiftoolPath,
+		"-n", "-all", "-json", "-api", "largefilesupport=1", tmpName,
+	).Output()
+	if err != nil {
+		return nil, nil, false
+	}
+
+	var arr []map[string]json.RawMessage
+	if err := json.Unmarshal(out, &arr); err != nil || len(arr) == 0 {
+		return nil, nil, false
+	}
+	m := arr[0]
+
+	dt := pickMetaDatetime(m)
+
+	// Strip temp-file artifacts and substitute the real name.
+	for _, k := range metaTempFileKeys {
+		delete(m, k)
+	}
+	if mtime == nil {
+		// Without a real source mtime this is just the temp file's write time.
+		delete(m, "FileModifyDate")
+	}
+	if originalName != "" {
+		if nb, err := json.Marshal(originalName); err == nil {
+			m["FileName"] = nb
+		}
+	} else {
+		delete(m, "FileName")
+	}
+
+	raw, err := json.Marshal(m)
+	if err != nil {
+		return nil, nil, false
+	}
+	return raw, dt, true
+}
+
+// pickMetaDatetime returns the first parseable content date among metaDateKeys.
+func pickMetaDatetime(m map[string]json.RawMessage) *time.Time {
+	for _, key := range metaDateKeys {
+		raw, ok := m[key]
+		if !ok {
+			continue
+		}
+		var s string
+		if err := json.Unmarshal(raw, &s); err != nil {
+			continue
+		}
+		if t, ok := parseExifDate(s); ok {
+			return &t
+		}
+	}
+	return nil
+}
+
+// parseExifDate parses exiftool's "YYYY:MM:DD HH:MM:SS" timestamps, with or
+// without a trailing timezone offset. Zeroed placeholders ("0000:00:00 ...")
+// fail to parse and are skipped by the caller.
+func parseExifDate(s string) (time.Time, bool) {
+	s = strings.TrimSpace(s)
+	for _, layout := range []string{
+		"2006:01:02 15:04:05-07:00",
+		"2006:01:02 15:04:05Z07:00",
+		"2006:01:02 15:04:05",
+	} {
+		if t, err := time.Parse(layout, s); err == nil {
+			return t, true
+		}
+	}
+	return time.Time{}, false
+}
+
+// extractEXIFWithDatetime is the pure-Go fallback used when exiftool is absent.
+// It parses EXIF from raw bytes (JPEG/TIFF only), returning both the JSON
+// representation and the DateTimeOriginal (if present). Both may be nil.
+func extractEXIFWithDatetime(data []byte) (json.RawMessage, *time.Time) {
+	x, err := exif.Decode(bytes.NewReader(data))
+	if err != nil {
+		return nil, nil
+	}
+	b, err := x.MarshalJSON()
+	if err != nil {
+		return nil, nil
+	}
+	var dt *time.Time
+	if t, err := x.DateTime(); err == nil {
+		dt = &t
+	}
+	return json.RawMessage(b), dt
+}

backend/internal/service/metadata_test.go

@@ -0,0 +1,110 @@
+package service
+
+import (
+	"bytes"
+	"encoding/json"
+	"image"
+	"image/color"
+	"image/png"
+	"testing"
+	"time"
+)
+
+func TestParseExifDate(t *testing.T) {
+	cases := []struct {
+		in   string
+		ok   bool
+		want time.Time
+	}{
+		{"2026:03:24 16:57:58", true, time.Date(2026, 3, 24, 16, 57, 58, 0, time.UTC)},
+		{"2026:05:08 23:07:55+03:00", true, time.Date(2026, 5, 8, 23, 7, 55, 0, time.FixedZone("", 3*3600))},
+		{"  2026:01:02 03:04:05  ", true, time.Date(2026, 1, 2, 3, 4, 5, 0, time.UTC)},
+		{"0000:00:00 00:00:00", false, time.Time{}},
+		{"not a date", false, time.Time{}},
+		{"", false, time.Time{}},
+	}
+	for _, c := range cases {
+		got, ok := parseExifDate(c.in)
+		if ok != c.ok {
+			t.Errorf("parseExifDate(%q) ok=%v, want %v", c.in, ok, c.ok)
+			continue
+		}
+		if ok && !got.Equal(c.want) {
+			t.Errorf("parseExifDate(%q) = %v, want %v", c.in, got, c.want)
+		}
+	}
+}
+
+// tinyPNG returns a valid 2x3 PNG with no embedded EXIF/date.
+func tinyPNG(t *testing.T) []byte {
+	t.Helper()
+	img := image.NewRGBA(image.Rect(0, 0, 2, 3))
+	img.Set(0, 0, color.RGBA{R: 10, G: 20, B: 30, A: 255})
+	var buf bytes.Buffer
+	if err := png.Encode(&buf, img); err != nil {
+		t.Fatalf("encode png: %v", err)
+	}
+	return buf.Bytes()
+}
+
+func TestExtractMetadataExiftool(t *testing.T) {
+	if exiftoolPath == "" {
+		t.Skip("exiftool not installed; metadata extraction falls back to goexif")
+	}
+
+	raw, dt := extractMetadata(tinyPNG(t), "snapshot.png", nil)
+	if raw == nil {
+		t.Fatal("expected non-nil metadata JSON")
+	}
+	if dt != nil {
+		t.Errorf("a PNG without a capture date should yield no content datetime, got %v", dt)
+	}
+
+	var m map[string]json.RawMessage
+	if err := json.Unmarshal(raw, &m); err != nil {
+		t.Fatalf("metadata is not valid JSON: %v", err)
+	}
+
+	// exiftool understood the format (goexif never would for PNG).
+	if v := jsonString(t, m, "FileType"); v != "PNG" {
+		t.Errorf("FileType = %q, want PNG", v)
+	}
+
+	// Dimensions are numeric, not human-readable strings.
+	for _, key := range []string{"ImageWidth", "ImageHeight"} {
+		raw, ok := m[key]
+		if !ok {
+			t.Errorf("missing %s", key)
+			continue
+		}
+		var n float64
+		if err := json.Unmarshal(raw, &n); err != nil {
+			t.Errorf("%s is not numeric: %s", key, raw)
+		}
+	}
+
+	// FileName is the original, not the temp file; temp-file artifacts are gone.
+	if v := jsonString(t, m, "FileName"); v != "snapshot.png" {
+		t.Errorf("FileName = %q, want snapshot.png", v)
+	}
+	for _, leaked := range []string{"SourceFile", "Directory", "FilePermissions", "FileModifyDate"} {
+		if _, ok := m[leaked]; ok {
+			t.Errorf("temp-file field %q should have been stripped", leaked)
+		}
+	}
+}
+
+func jsonString(t *testing.T, m map[string]json.RawMessage, key string) string {
+	t.Helper()
+	raw, ok := m[key]
+	if !ok {
+		t.Errorf("missing key %q", key)
+		return ""
+	}
+	var s string
+	if err := json.Unmarshal(raw, &s); err != nil {
+		t.Errorf("key %q is not a string: %s", key, raw)
+		return ""
+	}
+	return s
+}

backend/internal/service/pool_service.go

@@ -0,0 +1,251 @@
+package service
+
+import (
+	"context"
+	"encoding/json"
+
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+const poolObjectType = "pool"
+const poolObjectTypeID int16 = 4 // fourth row in 007_seed_data.sql object_types
+
+// PoolParams holds the fields for creating or patching a pool.
+type PoolParams struct {
+	Name     string
+	Notes    *string
+	Metadata json.RawMessage
+	IsPublic *bool
+}
+
+// PoolService handles pool CRUD and pool–file management with ACL + audit.
+type PoolService struct {
+	pools port.PoolRepo
+	acl   *ACLService
+	audit *AuditService
+}
+
+// NewPoolService creates a PoolService.
+func NewPoolService(
+	pools port.PoolRepo,
+	acl *ACLService,
+	audit *AuditService,
+) *PoolService {
+	return &PoolService{pools: pools, acl: acl, audit: audit}
+}
+
+// ---------------------------------------------------------------------------
+// CRUD
+// ---------------------------------------------------------------------------
+
+// List returns a paginated list of pools the caller may see.
+func (s *PoolService) List(ctx context.Context, params port.OffsetParams) (*domain.PoolOffsetPage, error) {
+	params.ViewerID, params.ViewerIsAdmin, _ = domain.UserFromContext(ctx)
+	return s.pools.List(ctx, params)
+}
+
+// Get returns a pool by ID, enforcing view ACL.
+func (s *PoolService) Get(ctx context.Context, id uuid.UUID) (*domain.Pool, error) {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+	p, err := s.pools.GetByID(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	ok, err := s.acl.CanView(ctx, userID, isAdmin, p.CreatorID, p.IsPublic, poolObjectTypeID, id)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		return nil, domain.ErrForbidden
+	}
+	return p, nil
+}
+
+// authorizeView returns nil if the caller may view the pool, else ErrForbidden
+// (or ErrNotFound if the pool does not exist).
+func (s *PoolService) authorizeView(ctx context.Context, poolID uuid.UUID) error {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+	p, err := s.pools.GetByID(ctx, poolID)
+	if err != nil {
+		return err
+	}
+	ok, err := s.acl.CanView(ctx, userID, isAdmin, p.CreatorID, p.IsPublic, poolObjectTypeID, poolID)
+	if err != nil {
+		return err
+	}
+	if !ok {
+		return domain.ErrForbidden
+	}
+	return nil
+}
+
+// RecordView appends a view-history entry for the current user, enforcing view
+// ACL (you can only record a view of a pool you may see).
+func (s *PoolService) RecordView(ctx context.Context, id uuid.UUID) error {
+	userID, _, _ := domain.UserFromContext(ctx)
+	if err := s.authorizeView(ctx, id); err != nil {
+		return err
+	}
+	return s.pools.RecordView(ctx, id, userID)
+}
+
+// authorizeEdit returns nil if the caller may edit the pool, else ErrForbidden
+// (or ErrNotFound if the pool does not exist).
+func (s *PoolService) authorizeEdit(ctx context.Context, poolID uuid.UUID) error {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+	p, err := s.pools.GetByID(ctx, poolID)
+	if err != nil {
+		return err
+	}
+	ok, err := s.acl.CanEdit(ctx, userID, isAdmin, p.CreatorID, poolObjectTypeID, poolID)
+	if err != nil {
+		return err
+	}
+	if !ok {
+		return domain.ErrForbidden
+	}
+	return nil
+}
+
+// Create inserts a new pool.
+func (s *PoolService) Create(ctx context.Context, p PoolParams) (*domain.Pool, error) {
+	userID, _, _ := domain.UserFromContext(ctx)
+
+	pool := &domain.Pool{
+		Name:      p.Name,
+		Notes:     p.Notes,
+		Metadata:  p.Metadata,
+		CreatorID: userID,
+	}
+	if p.IsPublic != nil {
+		pool.IsPublic = *p.IsPublic
+	}
+
+	created, err := s.pools.Create(ctx, pool)
+	if err != nil {
+		return nil, err
+	}
+
+	objType := poolObjectType
+	_ = s.audit.Log(ctx, "pool_create", &objType, &created.ID, nil)
+	return created, nil
+}
+
+// Update applies a partial patch to a pool.
+func (s *PoolService) Update(ctx context.Context, id uuid.UUID, p PoolParams) (*domain.Pool, error) {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+
+	current, err := s.pools.GetByID(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	ok, err := s.acl.CanEdit(ctx, userID, isAdmin, current.CreatorID, poolObjectTypeID, id)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		return nil, domain.ErrForbidden
+	}
+
+	patch := *current
+	if p.Name != "" {
+		patch.Name = p.Name
+	}
+	if p.Notes != nil {
+		patch.Notes = p.Notes
+	}
+	if len(p.Metadata) > 0 {
+		patch.Metadata = p.Metadata
+	}
+	if p.IsPublic != nil {
+		patch.IsPublic = *p.IsPublic
+	}
+
+	updated, err := s.pools.Update(ctx, id, &patch)
+	if err != nil {
+		return nil, err
+	}
+
+	objType := poolObjectType
+	_ = s.audit.Log(ctx, "pool_edit", &objType, &id, nil)
+	return updated, nil
+}
+
+// Delete removes a pool by ID, enforcing edit ACL.
+func (s *PoolService) Delete(ctx context.Context, id uuid.UUID) error {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+
+	pool, err := s.pools.GetByID(ctx, id)
+	if err != nil {
+		return err
+	}
+
+	ok, err := s.acl.CanEdit(ctx, userID, isAdmin, pool.CreatorID, poolObjectTypeID, id)
+	if err != nil {
+		return err
+	}
+	if !ok {
+		return domain.ErrForbidden
+	}
+
+	if err := s.pools.Delete(ctx, id); err != nil {
+		return err
+	}
+
+	objType := poolObjectType
+	_ = s.audit.Log(ctx, "pool_delete", &objType, &id, nil)
+	return nil
+}
+
+// ---------------------------------------------------------------------------
+// Pool–file operations
+// ---------------------------------------------------------------------------
+
+// ListFiles returns cursor-paginated files within a pool ordered by position,
+// enforcing view ACL on the pool.
+func (s *PoolService) ListFiles(ctx context.Context, poolID uuid.UUID, params port.PoolFileListParams) (*domain.PoolFilePage, error) {
+	if err := s.authorizeView(ctx, poolID); err != nil {
+		return nil, err
+	}
+	return s.pools.ListFiles(ctx, poolID, params)
+}
+
+// AddFiles adds files to a pool at the given position (nil = append), enforcing
+// edit ACL on the pool.
+func (s *PoolService) AddFiles(ctx context.Context, poolID uuid.UUID, fileIDs []uuid.UUID, position *int) error {
+	if err := s.authorizeEdit(ctx, poolID); err != nil {
+		return err
+	}
+	if err := s.pools.AddFiles(ctx, poolID, fileIDs, position); err != nil {
+		return err
+	}
+	objType := poolObjectType
+	_ = s.audit.Log(ctx, "file_pool_add", &objType, &poolID, map[string]any{"count": len(fileIDs)})
+	return nil
+}
+
+// RemoveFiles removes files from a pool, enforcing edit ACL on the pool.
+func (s *PoolService) RemoveFiles(ctx context.Context, poolID uuid.UUID, fileIDs []uuid.UUID) error {
+	if err := s.authorizeEdit(ctx, poolID); err != nil {
+		return err
+	}
+	if err := s.pools.RemoveFiles(ctx, poolID, fileIDs); err != nil {
+		return err
+	}
+	objType := poolObjectType
+	_ = s.audit.Log(ctx, "file_pool_remove", &objType, &poolID, map[string]any{"count": len(fileIDs)})
+	return nil
+}
+
+// Reorder sets the ordered sequence of file IDs within a pool, enforcing edit
+// ACL on the pool.
+func (s *PoolService) Reorder(ctx context.Context, poolID uuid.UUID, fileIDs []uuid.UUID) error {
+	if err := s.authorizeEdit(ctx, poolID); err != nil {
+		return err
+	}
+	return s.pools.Reorder(ctx, poolID, fileIDs)
+}

backend/internal/service/tag_service.go

@@ -0,0 +1,425 @@
+package service
+
+import (
+	"context"
+	"encoding/json"
+
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+const tagObjectType = "tag"
+const tagObjectTypeID int16 = 2 // second row in 007_seed_data.sql object_types
+
+// TagParams holds the fields for creating or patching a tag.
+type TagParams struct {
+	Name       string
+	Notes      *string
+	Color      *string    // nil = no change; pointer to empty string = clear
+	CategoryID *uuid.UUID // nil = no change; Nil UUID = unassign
+	Metadata   json.RawMessage
+	IsPublic   *bool
+}
+
+// TagService handles tag CRUD, tag-rule management, and file–tag operations
+// including automatic recursive rule application.
+type TagService struct {
+	tags  port.TagRepo
+	rules port.TagRuleRepo
+	acl   *ACLService
+	audit *AuditService
+	tx    port.Transactor
+}
+
+// NewTagService creates a TagService.
+func NewTagService(
+	tags port.TagRepo,
+	rules port.TagRuleRepo,
+	acl *ACLService,
+	audit *AuditService,
+	tx port.Transactor,
+) *TagService {
+	return &TagService{
+		tags:  tags,
+		rules: rules,
+		acl:   acl,
+		audit: audit,
+		tx:    tx,
+	}
+}
+
+// ---------------------------------------------------------------------------
+// Tag CRUD
+// ---------------------------------------------------------------------------
+
+// List returns a paginated, optionally filtered list of tags the caller may see.
+func (s *TagService) List(ctx context.Context, params port.OffsetParams) (*domain.TagOffsetPage, error) {
+	params.ViewerID, params.ViewerIsAdmin, _ = domain.UserFromContext(ctx)
+	return s.tags.List(ctx, params)
+}
+
+// Get returns a tag by ID, enforcing view ACL.
+func (s *TagService) Get(ctx context.Context, id uuid.UUID) (*domain.Tag, error) {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+	t, err := s.tags.GetByID(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+	ok, err := s.acl.CanView(ctx, userID, isAdmin, t.CreatorID, t.IsPublic, tagObjectTypeID, id)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		return nil, domain.ErrForbidden
+	}
+	return t, nil
+}
+
+// Create inserts a new tag record.
+func (s *TagService) Create(ctx context.Context, p TagParams) (*domain.Tag, error) {
+	userID, _, _ := domain.UserFromContext(ctx)
+
+	t := &domain.Tag{
+		Name:       p.Name,
+		Notes:      p.Notes,
+		Color:      p.Color,
+		CategoryID: p.CategoryID,
+		Metadata:   p.Metadata,
+		CreatorID:  userID,
+	}
+	if p.IsPublic != nil {
+		t.IsPublic = *p.IsPublic
+	}
+
+	created, err := s.tags.Create(ctx, t)
+	if err != nil {
+		return nil, err
+	}
+
+	objType := tagObjectType
+	_ = s.audit.Log(ctx, "tag_create", &objType, &created.ID, nil)
+	return created, nil
+}
+
+// Update applies a partial patch to a tag.
+// The service reads the current tag first so the caller only needs to supply
+// the fields that should change.
+func (s *TagService) Update(ctx context.Context, id uuid.UUID, p TagParams) (*domain.Tag, error) {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+
+	current, err := s.tags.GetByID(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	ok, err := s.acl.CanEdit(ctx, userID, isAdmin, current.CreatorID, tagObjectTypeID, id)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		return nil, domain.ErrForbidden
+	}
+
+	// Merge patch into current.
+	patch := *current // copy
+	if p.Name != "" {
+		patch.Name = p.Name
+	}
+	if p.Notes != nil {
+		patch.Notes = p.Notes
+	}
+	if p.Color != nil {
+		patch.Color = p.Color
+	}
+	if p.CategoryID != nil {
+		if *p.CategoryID == uuid.Nil {
+			patch.CategoryID = nil // explicit unassign
+		} else {
+			patch.CategoryID = p.CategoryID
+		}
+	}
+	if len(p.Metadata) > 0 {
+		patch.Metadata = p.Metadata
+	}
+	if p.IsPublic != nil {
+		patch.IsPublic = *p.IsPublic
+	}
+
+	updated, err := s.tags.Update(ctx, id, &patch)
+	if err != nil {
+		return nil, err
+	}
+
+	objType := tagObjectType
+	_ = s.audit.Log(ctx, "tag_edit", &objType, &id, nil)
+	return updated, nil
+}
+
+// Delete removes a tag by ID, enforcing edit ACL.
+func (s *TagService) Delete(ctx context.Context, id uuid.UUID) error {
+	userID, isAdmin, _ := domain.UserFromContext(ctx)
+
+	t, err := s.tags.GetByID(ctx, id)
+	if err != nil {
+		return err
+	}
+
+	ok, err := s.acl.CanEdit(ctx, userID, isAdmin, t.CreatorID, tagObjectTypeID, id)
+	if err != nil {
+		return err
+	}
+	if !ok {
+		return domain.ErrForbidden
+	}
+
+	if err := s.tags.Delete(ctx, id); err != nil {
+		return err
+	}
+
+	objType := tagObjectType
+	_ = s.audit.Log(ctx, "tag_delete", &objType, &id, nil)
+	return nil
+}
+
+// ---------------------------------------------------------------------------
+// Tag rules
+// ---------------------------------------------------------------------------
+
+// ListRules returns all rules for a tag (when this tag is applied, these follow).
+func (s *TagService) ListRules(ctx context.Context, tagID uuid.UUID) ([]domain.TagRule, error) {
+	return s.rules.ListByTag(ctx, tagID)
+}
+
+// CreateRule adds a tag rule. If applyToExisting is true, the then_tag is
+// retroactively applied to all files that already carry the when_tag.
+// Retroactive application requires a FileRepo; it is deferred until wired
+// in a future iteration (see port.FileRepo.ListByTag).
+func (s *TagService) CreateRule(ctx context.Context, whenTagID, thenTagID uuid.UUID, isActive, _ bool) (*domain.TagRule, error) {
+	return s.rules.Create(ctx, domain.TagRule{
+		WhenTagID: whenTagID,
+		ThenTagID: thenTagID,
+		IsActive:  isActive,
+	})
+}
+
+// SetRuleActive toggles a rule's is_active flag and returns the updated rule.
+// When active and applyToExisting are both true, the full transitive expansion
+// of thenTagID is retroactively applied to files already carrying whenTagID.
+func (s *TagService) SetRuleActive(ctx context.Context, whenTagID, thenTagID uuid.UUID, active, applyToExisting bool) (*domain.TagRule, error) {
+	if err := s.rules.SetActive(ctx, whenTagID, thenTagID, active, applyToExisting); err != nil {
+		return nil, err
+	}
+	rules, err := s.rules.ListByTag(ctx, whenTagID)
+	if err != nil {
+		return nil, err
+	}
+	for _, r := range rules {
+		if r.ThenTagID == thenTagID {
+			return &r, nil
+		}
+	}
+	return nil, domain.ErrNotFound
+}
+
+// DeleteRule removes a tag rule.
+func (s *TagService) DeleteRule(ctx context.Context, whenTagID, thenTagID uuid.UUID) error {
+	return s.rules.Delete(ctx, whenTagID, thenTagID)
+}
+
+// ---------------------------------------------------------------------------
+// File–tag operations (with auto-rule expansion)
+// ---------------------------------------------------------------------------
+
+// ListFileTags returns the tags on a file.
+func (s *TagService) ListFileTags(ctx context.Context, fileID uuid.UUID) ([]domain.Tag, error) {
+	return s.tags.ListByFile(ctx, fileID)
+}
+
+// SetFileTags replaces all tags on a file, then applies active rules for all
+// newly set tags (BFS expansion). Returns the full resulting tag set.
+func (s *TagService) SetFileTags(ctx context.Context, fileID uuid.UUID, tagIDs []uuid.UUID) ([]domain.Tag, error) {
+	expanded, err := s.expandTagSet(ctx, tagIDs)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := s.tags.SetFileTags(ctx, fileID, expanded); err != nil {
+		return nil, err
+	}
+
+	objType := fileObjectType
+	_ = s.audit.Log(ctx, "file_tag_add", &objType, &fileID, nil)
+	return s.tags.ListByFile(ctx, fileID)
+}
+
+// AddFileTag adds a single tag to a file, then recursively applies active rules.
+// Returns the full resulting tag set.
+func (s *TagService) AddFileTag(ctx context.Context, fileID, tagID uuid.UUID) ([]domain.Tag, error) {
+	// Compute the full set including rule-expansion from tagID.
+	extra, err := s.expandTagSet(ctx, []uuid.UUID{tagID})
+	if err != nil {
+		return nil, err
+	}
+
+	// Fetch current tags so we don't lose them.
+	current, err := s.tags.ListByFile(ctx, fileID)
+	if err != nil {
+		return nil, err
+	}
+
+	// Union: existing + expanded new tags.
+	seen := make(map[uuid.UUID]bool, len(current)+len(extra))
+	for _, t := range current {
+		seen[t.ID] = true
+	}
+	merged := make([]uuid.UUID, len(current))
+	for i, t := range current {
+		merged[i] = t.ID
+	}
+	for _, id := range extra {
+		if !seen[id] {
+			seen[id] = true
+			merged = append(merged, id)
+		}
+	}
+
+	if err := s.tags.SetFileTags(ctx, fileID, merged); err != nil {
+		return nil, err
+	}
+
+	objType := fileObjectType
+	_ = s.audit.Log(ctx, "file_tag_add", &objType, &fileID, map[string]any{"tag_id": tagID})
+	return s.tags.ListByFile(ctx, fileID)
+}
+
+// RemoveFileTag removes a single tag from a file.
+func (s *TagService) RemoveFileTag(ctx context.Context, fileID, tagID uuid.UUID) error {
+	if err := s.tags.RemoveFileTag(ctx, fileID, tagID); err != nil {
+		return err
+	}
+
+	objType := fileObjectType
+	_ = s.audit.Log(ctx, "file_tag_remove", &objType, &fileID, map[string]any{"tag_id": tagID})
+	return nil
+}
+
+// BulkSetTags adds or removes tags on multiple files (with rule expansion for add).
+// Returns the tagIDs that were applied (the expanded input set for add; empty for remove).
+func (s *TagService) BulkSetTags(ctx context.Context, fileIDs []uuid.UUID, action string, tagIDs []uuid.UUID) ([]uuid.UUID, error) {
+	if action != "add" && action != "remove" {
+		return nil, domain.ErrValidation
+	}
+
+	// Pre-expand tag set once; all files get the same expansion.
+	var expanded []uuid.UUID
+	if action == "add" {
+		var err error
+		expanded, err = s.expandTagSet(ctx, tagIDs)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	for _, fileID := range fileIDs {
+		switch action {
+		case "add":
+			current, err := s.tags.ListByFile(ctx, fileID)
+			if err != nil {
+				if err == domain.ErrNotFound {
+					continue
+				}
+				return nil, err
+			}
+			seen := make(map[uuid.UUID]bool, len(current))
+			merged := make([]uuid.UUID, len(current))
+			for i, t := range current {
+				seen[t.ID] = true
+				merged[i] = t.ID
+			}
+			for _, id := range expanded {
+				if !seen[id] {
+					seen[id] = true
+					merged = append(merged, id)
+				}
+			}
+			if err := s.tags.SetFileTags(ctx, fileID, merged); err != nil {
+				return nil, err
+			}
+		case "remove":
+			current, err := s.tags.ListByFile(ctx, fileID)
+			if err != nil {
+				if err == domain.ErrNotFound {
+					continue
+				}
+				return nil, err
+			}
+			remove := make(map[uuid.UUID]bool, len(tagIDs))
+			for _, id := range tagIDs {
+				remove[id] = true
+			}
+			kept := make([]uuid.UUID, 0, len(current))
+			for _, t := range current {
+				if !remove[t.ID] {
+					kept = append(kept, t.ID)
+				}
+			}
+			if err := s.tags.SetFileTags(ctx, fileID, kept); err != nil {
+				return nil, err
+			}
+		}
+	}
+
+	if action == "add" {
+		return expanded, nil
+	}
+	return []uuid.UUID{}, nil
+}
+
+// CommonTags returns tags present on ALL given files and tags present on SOME.
+func (s *TagService) CommonTags(ctx context.Context, fileIDs []uuid.UUID) (common, partial []domain.Tag, err error) {
+	common, err = s.tags.CommonTagsForFiles(ctx, fileIDs)
+	if err != nil {
+		return nil, nil, err
+	}
+	partial, err = s.tags.PartialTagsForFiles(ctx, fileIDs)
+	if err != nil {
+		return nil, nil, err
+	}
+	return common, partial, nil
+}
+
+// ---------------------------------------------------------------------------
+// Internal helpers
+// ---------------------------------------------------------------------------
+
+// expandTagSet runs a BFS from the given seed tags, following active tag rules,
+// and returns the full set of tag IDs that should be applied (seeds + auto-applied).
+func (s *TagService) expandTagSet(ctx context.Context, seeds []uuid.UUID) ([]uuid.UUID, error) {
+	visited := make(map[uuid.UUID]bool, len(seeds))
+	queue := make([]uuid.UUID, 0, len(seeds))
+
+	for _, id := range seeds {
+		if !visited[id] {
+			visited[id] = true
+			queue = append(queue, id)
+		}
+	}
+
+	for i := 0; i < len(queue); i++ {
+		tagID := queue[i]
+		rules, err := s.rules.ListByTag(ctx, tagID)
+		if err != nil {
+			return nil, err
+		}
+		for _, r := range rules {
+			if r.IsActive && !visited[r.ThenTagID] {
+				visited[r.ThenTagID] = true
+				queue = append(queue, r.ThenTagID)
+			}
+		}
+	}
+
+	return queue, nil
+}

backend/internal/service/user_service.go

@@ -0,0 +1,192 @@
+package service
+
+import (
+	"context"
+	"errors"
+	"fmt"
+
+	"golang.org/x/crypto/bcrypt"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+// UserService handles user CRUD and profile management.
+type UserService struct {
+	users    port.UserRepo
+	sessions port.SessionRepo
+	audit    *AuditService
+}
+
+// NewUserService creates a UserService.
+func NewUserService(users port.UserRepo, sessions port.SessionRepo, audit *AuditService) *UserService {
+	return &UserService{users: users, sessions: sessions, audit: audit}
+}
+
+// EnsureAdmin creates the initial administrator account if it does not already
+// exist. It is idempotent and never overwrites an existing user's password, so
+// an operator who has changed the admin password keeps it across restarts.
+func (s *UserService) EnsureAdmin(ctx context.Context, username, password string) error {
+	if username == "" || password == "" {
+		return fmt.Errorf("EnsureAdmin: username and password must be set")
+	}
+
+	if _, err := s.users.GetByName(ctx, username); err == nil {
+		return nil // already exists
+	} else if !errors.Is(err, domain.ErrNotFound) {
+		return fmt.Errorf("EnsureAdmin: lookup: %w", err)
+	}
+
+	hash, err := bcrypt.GenerateFromPassword([]byte(password), bcrypt.DefaultCost)
+	if err != nil {
+		return fmt.Errorf("EnsureAdmin: hash: %w", err)
+	}
+	_, err = s.users.Create(ctx, &domain.User{
+		Name:      username,
+		Password:  string(hash),
+		IsAdmin:   true,
+		CanCreate: true,
+	})
+	if err != nil {
+		return fmt.Errorf("EnsureAdmin: create: %w", err)
+	}
+	return nil
+}
+
+// ---------------------------------------------------------------------------
+// Self-service
+// ---------------------------------------------------------------------------
+
+// GetMe returns the profile of the currently authenticated user.
+func (s *UserService) GetMe(ctx context.Context) (*domain.User, error) {
+	userID, _, _ := domain.UserFromContext(ctx)
+	return s.users.GetByID(ctx, userID)
+}
+
+// UpdateMeParams holds fields a user may change on their own profile.
+type UpdateMeParams struct {
+	Name     string  // empty = no change
+	Password *string // nil = no change
+}
+
+// UpdateMe allows a user to change their own name and/or password.
+func (s *UserService) UpdateMe(ctx context.Context, p UpdateMeParams) (*domain.User, error) {
+	userID, _, _ := domain.UserFromContext(ctx)
+
+	current, err := s.users.GetByID(ctx, userID)
+	if err != nil {
+		return nil, err
+	}
+
+	patch := *current
+	if p.Name != "" {
+		patch.Name = p.Name
+	}
+	if p.Password != nil {
+		hash, err := bcrypt.GenerateFromPassword([]byte(*p.Password), bcrypt.DefaultCost)
+		if err != nil {
+			return nil, fmt.Errorf("UserService.UpdateMe hash: %w", err)
+		}
+		patch.Password = string(hash)
+	}
+
+	return s.users.Update(ctx, userID, &patch)
+}
+
+// ---------------------------------------------------------------------------
+// Admin CRUD
+// ---------------------------------------------------------------------------
+
+// List returns a paginated list of users (admin only — caller must enforce).
+func (s *UserService) List(ctx context.Context, params port.OffsetParams) (*domain.UserPage, error) {
+	return s.users.List(ctx, params)
+}
+
+// Get returns a user by ID (admin only).
+func (s *UserService) Get(ctx context.Context, id int16) (*domain.User, error) {
+	return s.users.GetByID(ctx, id)
+}
+
+// CreateParams holds fields for creating a new user.
+type CreateUserParams struct {
+	Name      string
+	Password  string
+	IsAdmin   bool
+	CanCreate bool
+}
+
+// Create inserts a new user with a bcrypt-hashed password (admin only).
+func (s *UserService) Create(ctx context.Context, p CreateUserParams) (*domain.User, error) {
+	hash, err := bcrypt.GenerateFromPassword([]byte(p.Password), bcrypt.DefaultCost)
+	if err != nil {
+		return nil, fmt.Errorf("UserService.Create hash: %w", err)
+	}
+
+	u := &domain.User{
+		Name:      p.Name,
+		Password:  string(hash),
+		IsAdmin:   p.IsAdmin,
+		CanCreate: p.CanCreate,
+	}
+	created, err := s.users.Create(ctx, u)
+	if err != nil {
+		return nil, err
+	}
+
+	_ = s.audit.Log(ctx, "user_create", nil, nil, map[string]any{"target_user_id": created.ID})
+	return created, nil
+}
+
+// UpdateAdminParams holds fields an admin may change on any user.
+type UpdateAdminParams struct {
+	IsAdmin   *bool
+	CanCreate *bool
+	IsBlocked *bool
+}
+
+// UpdateAdmin applies an admin-level patch to a user.
+func (s *UserService) UpdateAdmin(ctx context.Context, id int16, p UpdateAdminParams) (*domain.User, error) {
+	current, err := s.users.GetByID(ctx, id)
+	if err != nil {
+		return nil, err
+	}
+
+	patch := *current
+	if p.IsAdmin != nil {
+		patch.IsAdmin = *p.IsAdmin
+	}
+	if p.CanCreate != nil {
+		patch.CanCreate = *p.CanCreate
+	}
+	if p.IsBlocked != nil {
+		patch.IsBlocked = *p.IsBlocked
+	}
+
+	updated, err := s.users.Update(ctx, id, &patch)
+	if err != nil {
+		return nil, err
+	}
+
+	// Log block/unblock specifically, and revoke all sessions on block so the
+	// user's outstanding access tokens stop working immediately.
+	if p.IsBlocked != nil {
+		action := "user_unblock"
+		if *p.IsBlocked {
+			action = "user_block"
+			if err := s.sessions.DeleteByUserID(ctx, id); err != nil {
+				return nil, fmt.Errorf("UserService.UpdateAdmin revoke sessions: %w", err)
+			}
+		}
+		_ = s.audit.Log(ctx, action, nil, nil, map[string]any{"target_user_id": id})
+	}
+	return updated, nil
+}
+
+// Delete removes a user by ID (admin only).
+func (s *UserService) Delete(ctx context.Context, id int16) error {
+	if err := s.users.Delete(ctx, id); err != nil {
+		return err
+	}
+	_ = s.audit.Log(ctx, "user_delete", nil, nil, map[string]any{"target_user_id": id})
+	return nil
+}

backend/internal/storage/disk.go

@@ -0,0 +1,397 @@
+// Package storage provides a local-filesystem implementation of port.FileStorage.
+package storage
+
+import (
+	"bytes"
+	"context"
+	"fmt"
+	_ "golang.org/x/image/webp" // register WebP decoder
+	"image"
+	"image/color"
+	_ "image/gif" // register GIF decoder
+	"image/jpeg"
+	_ "image/png" // register PNG decoder
+	"io"
+	"os"
+	"os/exec"
+	"path/filepath"
+	"runtime"
+	"time"
+
+	"github.com/disintegration/imaging"
+	"github.com/google/uuid"
+
+	"tanabata/backend/internal/domain"
+	"tanabata/backend/internal/port"
+)
+
+// DiskStorage implements port.FileStorage using the local filesystem.
+//
+// Directory layout:
+//
+//	{filesPath}/{id}                — original file (UUID basename, no extension)
+//	{thumbsPath}/{id}_thumb.jpg     — thumbnail cache
+//	{thumbsPath}/{id}_preview.jpg   — preview cache
+type DiskStorage struct {
+	filesPath     string
+	thumbsPath    string
+	thumbWidth    int
+	thumbHeight   int
+	previewWidth  int
+	previewHeight int
+	maxPixels     int
+	// genSem bounds concurrent thumbnail/preview generation. Each resize already
+	// fans out across every core (imaging uses GOMAXPROCS), and large sources cost
+	// hundreds of MB to decode, so unbounded parallelism on a burst of big images
+	// pegs the CPU and can exhaust RAM. A buffered channel caps how many run at once.
+	genSem chan struct{}
+}
+
+var _ port.FileStorage = (*DiskStorage)(nil)
+
+// NewDiskStorage creates a DiskStorage and ensures both directories exist.
+//
+// maxPixels caps the source pixel count we will decode in-process (0 → a sane
+// default). concurrency bounds simultaneous generation (≤0 → half the CPUs).
+func NewDiskStorage(
+	filesPath, thumbsPath string,
+	thumbW, thumbH, prevW, prevH int,
+	maxPixels, concurrency int,
+) (*DiskStorage, error) {
+	for _, p := range []string{filesPath, thumbsPath} {
+		if err := os.MkdirAll(p, 0o755); err != nil {
+			return nil, fmt.Errorf("storage: create directory %q: %w", p, err)
+		}
+	}
+	if maxPixels <= 0 {
+		maxPixels = defaultMaxDecodePixels
+	}
+	if concurrency <= 0 {
+		concurrency = max(1, runtime.GOMAXPROCS(0)/2)
+	}
+	return &DiskStorage{
+		filesPath:     filesPath,
+		thumbsPath:    thumbsPath,
+		thumbWidth:    thumbW,
+		thumbHeight:   thumbH,
+		previewWidth:  prevW,
+		previewHeight: prevH,
+		maxPixels:     maxPixels,
+		genSem:        make(chan struct{}, concurrency),
+	}, nil
+}
+
+// ---------------------------------------------------------------------------
+// port.FileStorage implementation
+// ---------------------------------------------------------------------------
+
+// Save writes r to {filesPath}/{id} and returns the number of bytes written.
+func (s *DiskStorage) Save(_ context.Context, id uuid.UUID, r io.Reader) (int64, error) {
+	dst := s.originalPath(id)
+	f, err := os.Create(dst)
+	if err != nil {
+		return 0, fmt.Errorf("storage.Save create %q: %w", dst, err)
+	}
+	n, copyErr := io.Copy(f, r)
+	closeErr := f.Close()
+	if copyErr != nil {
+		os.Remove(dst)
+		return 0, fmt.Errorf("storage.Save write: %w", copyErr)
+	}
+	if closeErr != nil {
+		os.Remove(dst)
+		return 0, fmt.Errorf("storage.Save close: %w", closeErr)
+	}
+	return n, nil
+}
+
+// Read opens the original file for reading. The caller must close the result.
+func (s *DiskStorage) Read(_ context.Context, id uuid.UUID) (io.ReadCloser, error) {
+	f, err := os.Open(s.originalPath(id))
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("storage.Read: %w", err)
+	}
+	return f, nil
+}
+
+// Delete removes the original file. Returns ErrNotFound if it does not exist.
+func (s *DiskStorage) Delete(_ context.Context, id uuid.UUID) error {
+	if err := os.Remove(s.originalPath(id)); err != nil {
+		if os.IsNotExist(err) {
+			return domain.ErrNotFound
+		}
+		return fmt.Errorf("storage.Delete: %w", err)
+	}
+	return nil
+}
+
+// InvalidateCache removes the cached thumbnail and preview for id, if present,
+// so they are regenerated from the current file content on the next request.
+func (s *DiskStorage) InvalidateCache(_ context.Context, id uuid.UUID) error {
+	for _, p := range []string{s.thumbCachePath(id), s.previewCachePath(id)} {
+		if err := os.Remove(p); err != nil && !os.IsNotExist(err) {
+			return fmt.Errorf("storage.InvalidateCache remove %q: %w", p, err)
+		}
+	}
+	return nil
+}
+
+// Thumbnail returns a JPEG scaled to fit within the configured max width×height,
+// preserving the original aspect ratio (never upscaled, never cropped); the grid
+// cell letterboxes it as needed. Generated on first call and cached. Video files
+// are thumbnailed via ffmpeg; other non-image files get a placeholder.
+func (s *DiskStorage) Thumbnail(ctx context.Context, id uuid.UUID) (io.ReadCloser, error) {
+	return s.serveGenerated(ctx, id, s.thumbCachePath(id), s.thumbWidth, s.thumbHeight)
+}
+
+// Preview returns a JPEG scaled to fit within the configured max width×height,
+// preserving the original aspect ratio (never upscaled, never cropped) so the
+// viewer shows the whole image. Generated on first call and cached. Video files
+// are thumbnailed via ffmpeg; other non-image files get a placeholder.
+func (s *DiskStorage) Preview(ctx context.Context, id uuid.UUID) (io.ReadCloser, error) {
+	return s.serveGenerated(ctx, id, s.previewCachePath(id), s.previewWidth, s.previewHeight)
+}
+
+// ---------------------------------------------------------------------------
+// Internal helpers
+// ---------------------------------------------------------------------------
+
+// serveGenerated is the shared implementation for Thumbnail and Preview. Both
+// fit the source within maxW×maxH preserving the aspect ratio (no crop, no
+// upscale); they differ only in the configured dimensions.
+//
+// Resolution order:
+//  1. Return cached JPEG if present.
+//  2. vipsthumbnail (shrink-on-load; the primary still-image path).
+//  3. Pure-Go decode + imaging.Fit (fallback when vips is absent).
+//  4. Extract a frame with ffmpeg (video files).
+//  5. Solid-colour placeholder (archives, unrecognised formats, etc.).
+func (s *DiskStorage) serveGenerated(ctx context.Context, id uuid.UUID, cachePath string, maxW, maxH int) (io.ReadCloser, error) {
+	// Fast path: cache hit.
+	if f, err := os.Open(cachePath); err == nil {
+		return f, nil
+	}
+
+	// Verify the original file exists before doing any work.
+	srcPath := s.originalPath(id)
+	if _, err := os.Stat(srcPath); err != nil {
+		if os.IsNotExist(err) {
+			return nil, domain.ErrNotFound
+		}
+		return nil, fmt.Errorf("storage: stat %q: %w", srcPath, err)
+	}
+
+	// Bound concurrent generation so a burst of large images can't peg every core
+	// or exhaust RAM. Queue here (respecting cancellation) rather than starting
+	// the heavy decode immediately.
+	select {
+	case s.genSem <- struct{}{}:
+		defer func() { <-s.genSem }()
+	case <-ctx.Done():
+		return nil, ctx.Err()
+	}
+
+	// Another request may have generated this while we waited on the semaphore.
+	if f, err := os.Open(cachePath); err == nil {
+		return f, nil
+	}
+
+	// Primary path: vipsthumbnail. It shrinks on load (e.g. JPEG DCT scaling), so
+	// even a 200+ Mpx photo is thumbnailed in a fraction of the memory and CPU of a
+	// full in-process decode, writing the final JPEG straight to the cache. Falls
+	// through when vips is absent or can't read the source (e.g. a video).
+	if vipsThumbnailPath != "" {
+		if rc, err := s.vipsThumbnail(ctx, srcPath, cachePath, maxW, maxH); err == nil {
+			return rc, nil
+		}
+	}
+
+	// Fallback pipeline (pure Go):
+	//  1. Still-image decode (JPEG/PNG/GIF), rejecting oversized rasters.
+	//  2. Video frame extraction via ffmpeg.
+	//  3. Solid-colour placeholder.
+	var img image.Image
+	if decoded, err := decodeImageLimited(srcPath, s.maxPixels); err == nil {
+		img = imaging.Fit(decoded, maxW, maxH, imaging.Lanczos)
+	} else if frame, err := extractVideoFrame(ctx, srcPath); err == nil {
+		img = imaging.Fit(frame, maxW, maxH, imaging.Lanczos)
+	} else {
+		img = placeholder(maxW, maxH)
+	}
+
+	// Write to cache atomically (temp→rename) and return an open reader.
+	if rc, err := writeCache(cachePath, img); err == nil {
+		return rc, nil
+	}
+
+	// Cache write failed (read-only fs, disk full, …). Serve from an
+	// in-memory buffer so the request still succeeds.
+	var buf bytes.Buffer
+	if err := jpeg.Encode(&buf, img, &jpeg.Options{Quality: 85}); err != nil {
+		return nil, fmt.Errorf("storage: encode in-memory JPEG: %w", err)
+	}
+	return io.NopCloser(&buf), nil
+}
+
+// writeCache encodes img as JPEG to cachePath via an atomic temp→rename write,
+// then opens and returns the cache file.
+func writeCache(cachePath string, img image.Image) (io.ReadCloser, error) {
+	dir := filepath.Dir(cachePath)
+	tmp, err := os.CreateTemp(dir, ".cache-*.tmp")
+	if err != nil {
+		return nil, fmt.Errorf("storage: create temp file: %w", err)
+	}
+	tmpName := tmp.Name()
+
+	encErr := jpeg.Encode(tmp, img, &jpeg.Options{Quality: 85})
+	closeErr := tmp.Close()
+	if encErr != nil {
+		os.Remove(tmpName)
+		return nil, fmt.Errorf("storage: encode cache JPEG: %w", encErr)
+	}
+	if closeErr != nil {
+		os.Remove(tmpName)
+		return nil, fmt.Errorf("storage: close temp file: %w", closeErr)
+	}
+	if err := os.Rename(tmpName, cachePath); err != nil {
+		os.Remove(tmpName)
+		return nil, fmt.Errorf("storage: rename cache file: %w", err)
+	}
+	f, err := os.Open(cachePath)
+	if err != nil {
+		return nil, fmt.Errorf("storage: open cache file: %w", err)
+	}
+	return f, nil
+}
+
+// defaultMaxDecodePixels is the fallback cap when none is configured. It bounds
+// the cost of a decompression bomb (a tiny file that expands to an enormous
+// raster) and the per-image memory; ~300 Mpx covers e.g. a 13000×17000 photo.
+const defaultMaxDecodePixels = 300_000_000
+
+// decodeImageLimited decodes the image at path after first inspecting its header
+// dimensions via image.DecodeConfig (which does not allocate the raster), and
+// refuses images whose pixel count exceeds maxPixels.
+func decodeImageLimited(path string, maxPixels int) (image.Image, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, err
+	}
+	defer f.Close()
+
+	cfg, _, err := image.DecodeConfig(f)
+	if err != nil {
+		return nil, err
+	}
+	if int64(cfg.Width)*int64(cfg.Height) > int64(maxPixels) {
+		return nil, fmt.Errorf("image too large to decode: %dx%d", cfg.Width, cfg.Height)
+	}
+	if _, err := f.Seek(0, io.SeekStart); err != nil {
+		return nil, err
+	}
+	return imaging.Decode(f, imaging.AutoOrientation(true))
+}
+
+// vipsThumbnailPath is the resolved path to the vipsthumbnail CLI, or "" when it
+// isn't installed — in which case generation falls back to the pure-Go pipeline.
+var vipsThumbnailPath, _ = exec.LookPath("vipsthumbnail")
+
+// vipsThumbnail generates a JPEG thumbnail with the vipsthumbnail CLI, writing it
+// straight to cachePath via an atomic temp→rename. vips decodes large images at a
+// reduced scale (shrink-on-load), so this costs a fraction of the memory and CPU
+// of a full in-process decode. The result is fit within maxW×maxH and never
+// upscaled (the ">" size modifier). Returns an error for inputs vips can't read
+// (e.g. videos) so the caller can fall back.
+func (s *DiskStorage) vipsThumbnail(ctx context.Context, srcPath, cachePath string, maxW, maxH int) (io.ReadCloser, error) {
+	ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
+	defer cancel()
+
+	tmp, err := os.CreateTemp(filepath.Dir(cachePath), ".vips-*.jpg")
+	if err != nil {
+		return nil, fmt.Errorf("storage: create temp file: %w", err)
+	}
+	tmpName := tmp.Name()
+	_ = tmp.Close()
+
+	cmd := exec.CommandContext(ctx, vipsThumbnailPath,
+		srcPath,
+		"--size", fmt.Sprintf("%dx%d>", maxW, maxH),
+		"--output", tmpName+"[Q=85]",
+	)
+	cmd.Stderr = io.Discard
+
+	if err := cmd.Run(); err != nil {
+		os.Remove(tmpName)
+		return nil, fmt.Errorf("vipsthumbnail: %w", err)
+	}
+	if fi, err := os.Stat(tmpName); err != nil || fi.Size() == 0 {
+		os.Remove(tmpName)
+		return nil, fmt.Errorf("vipsthumbnail: no output produced")
+	}
+	if err := os.Rename(tmpName, cachePath); err != nil {
+		os.Remove(tmpName)
+		return nil, fmt.Errorf("storage: rename cache file: %w", err)
+	}
+	f, err := os.Open(cachePath)
+	if err != nil {
+		return nil, fmt.Errorf("storage: open cache file: %w", err)
+	}
+	return f, nil
+}
+
+// extractVideoFrame uses ffmpeg to extract a single frame from a video file.
+// It seeks 1 second in (keyframe-accurate fast seek) and pipes the frame out
+// as PNG. If the video is shorter than 1 s the seek is silently ignored by
+// ffmpeg and the first available frame is returned instead.
+// Returns an error if ffmpeg is not installed or produces no output. The run is
+// bounded by a timeout so a malformed file cannot hang the request indefinitely.
+func extractVideoFrame(ctx context.Context, srcPath string) (image.Image, error) {
+	ctx, cancel := context.WithTimeout(ctx, 30*time.Second)
+	defer cancel()
+
+	var out bytes.Buffer
+	cmd := exec.CommandContext(ctx, "ffmpeg",
+		"-ss", "1", // fast input seek; ignored gracefully on short files
+		"-i", srcPath,
+		"-vframes", "1",
+		"-f", "image2",
+		"-vcodec", "png",
+		"pipe:1",
+	)
+	cmd.Stdout = &out
+	cmd.Stderr = io.Discard // suppress ffmpeg progress output
+
+	if err := cmd.Run(); err != nil || out.Len() == 0 {
+		return nil, fmt.Errorf("ffmpeg frame extract: %w", err)
+	}
+	return imaging.Decode(&out)
+}
+
+// ---------------------------------------------------------------------------
+// Path helpers
+// ---------------------------------------------------------------------------
+
+func (s *DiskStorage) originalPath(id uuid.UUID) string {
+	return filepath.Join(s.filesPath, id.String())
+}
+
+func (s *DiskStorage) thumbCachePath(id uuid.UUID) string {
+	return filepath.Join(s.thumbsPath, id.String()+"_thumb.jpg")
+}
+
+func (s *DiskStorage) previewCachePath(id uuid.UUID) string {
+	return filepath.Join(s.thumbsPath, id.String()+"_preview.jpg")
+}
+
+// ---------------------------------------------------------------------------
+// Image helpers
+// ---------------------------------------------------------------------------
+
+// placeholder returns a solid-colour image of size w×h for files that cannot
+// be decoded as images. Uses #444455 from the design palette.
+func placeholder(w, h int) *image.NRGBA {
+	return imaging.New(w, h, color.NRGBA{R: 0x44, G: 0x44, B: 0x55, A: 0xFF})
+}

backend/internal/storage/disk_test.go

@@ -0,0 +1,181 @@
+package storage
+
+import (
+	"bytes"
+	"context"
+	"image"
+	"image/color"
+	"image/png"
+	"io"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/disintegration/imaging"
+	"github.com/google/uuid"
+)
+
+// writeTestImage writes a w×h PNG filled with a distinct (non-placeholder)
+// colour so a generated thumbnail can be told apart from the grey placeholder.
+func writeTestImage(t *testing.T, path string, w, h int) {
+	t.Helper()
+	img := image.NewNRGBA(image.Rect(0, 0, w, h))
+	for y := 0; y < h; y++ {
+		for x := 0; x < w; x++ {
+			img.Set(x, y, color.NRGBA{R: 0xC0, G: 0x10, B: 0x20, A: 0xFF})
+		}
+	}
+	f, err := os.Create(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer f.Close()
+	if err := png.Encode(f, img); err != nil {
+		t.Fatal(err)
+	}
+}
+
+func TestDecodeImageLimited(t *testing.T) {
+	dir := t.TempDir()
+	p := filepath.Join(dir, "img.png")
+	writeTestImage(t, p, 100, 80) // 8000 px
+
+	if _, err := decodeImageLimited(p, 4000); err == nil {
+		t.Fatal("expected rejection for an image over the pixel cap")
+	}
+
+	img, err := decodeImageLimited(p, 100000)
+	if err != nil {
+		t.Fatalf("expected decode within the cap, got %v", err)
+	}
+	if b := img.Bounds(); b.Dx() != 100 || b.Dy() != 80 {
+		t.Fatalf("unexpected decoded size %v", b.Size())
+	}
+}
+
+// TestThumbnailGeneratesAndCaches exercises the full generation path (semaphore
+// acquire → decode → fit → encode → cache) and the cache fast path on re-request.
+func TestThumbnailGeneratesAndCaches(t *testing.T) {
+	files := t.TempDir()
+	thumbs := t.TempDir()
+	id := uuid.New()
+	writeTestImage(t, filepath.Join(files, id.String()), 100, 80)
+
+	s, err := NewDiskStorage(files, thumbs, 160, 160, 1920, 1080, 0, 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rc, err := s.Thumbnail(context.Background(), id)
+	if err != nil {
+		t.Fatalf("Thumbnail: %v", err)
+	}
+	data, _ := io.ReadAll(rc)
+	rc.Close()
+
+	out, err := imaging.Decode(bytes.NewReader(data))
+	if err != nil {
+		t.Fatalf("decode thumbnail: %v", err)
+	}
+	// The source fits within 160×160, so it is not upscaled.
+	if b := out.Bounds(); b.Dx() != 100 || b.Dy() != 80 {
+		t.Fatalf("unexpected thumbnail size %v", b.Size())
+	}
+	// Centre pixel should be the source's red, not the grey placeholder.
+	r, g, b, _ := out.At(50, 40).RGBA()
+	if !(r>>8 > g>>8+40 && r>>8 > b>>8+40) {
+		t.Fatalf("thumbnail is not the source image (got r=%d g=%d b=%d) — fell back to placeholder?", r>>8, g>>8, b>>8)
+	}
+
+	// The cache file must now exist, and a second request must serve it.
+	if _, err := os.Stat(s.thumbCachePath(id)); err != nil {
+		t.Fatalf("cache file not written: %v", err)
+	}
+	rc2, err := s.Thumbnail(context.Background(), id)
+	if err != nil {
+		t.Fatalf("Thumbnail (cached): %v", err)
+	}
+	rc2.Close()
+}
+
+// TestThumbnailFallbackWithoutVips forces the pure-Go pipeline (as if vips were
+// not installed) and verifies generation still produces the source image.
+func TestThumbnailFallbackWithoutVips(t *testing.T) {
+	orig := vipsThumbnailPath
+	vipsThumbnailPath = ""
+	t.Cleanup(func() { vipsThumbnailPath = orig })
+
+	files := t.TempDir()
+	thumbs := t.TempDir()
+	id := uuid.New()
+	writeTestImage(t, filepath.Join(files, id.String()), 100, 80)
+
+	s, err := NewDiskStorage(files, thumbs, 160, 160, 1920, 1080, 0, 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rc, err := s.Thumbnail(context.Background(), id)
+	if err != nil {
+		t.Fatalf("Thumbnail: %v", err)
+	}
+	data, _ := io.ReadAll(rc)
+	rc.Close()
+
+	out, err := imaging.Decode(bytes.NewReader(data))
+	if err != nil {
+		t.Fatalf("decode thumbnail: %v", err)
+	}
+	if b := out.Bounds(); b.Dx() != 100 || b.Dy() != 80 {
+		t.Fatalf("unexpected thumbnail size %v", b.Size())
+	}
+	r, g, b, _ := out.At(50, 40).RGBA()
+	if !(r>>8 > g>>8+40 && r>>8 > b>>8+40) {
+		t.Fatalf("fallback produced a placeholder, not the source (r=%d g=%d b=%d)", r>>8, g>>8, b>>8)
+	}
+}
+
+// TestPreviewGeneratesAndCaches verifies Preview runs through the same pipeline
+// with the preview dimensions and its own cache file (not the thumbnail's).
+func TestPreviewGeneratesAndCaches(t *testing.T) {
+	files := t.TempDir()
+	thumbs := t.TempDir()
+	id := uuid.New()
+	// Larger than the thumbnail box but within the preview box, so the preview
+	// keeps full resolution where a thumbnail would shrink it.
+	writeTestImage(t, filepath.Join(files, id.String()), 400, 300)
+
+	s, err := NewDiskStorage(files, thumbs, 160, 160, 1920, 1080, 0, 1)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	rc, err := s.Preview(context.Background(), id)
+	if err != nil {
+		t.Fatalf("Preview: %v", err)
+	}
+	data, _ := io.ReadAll(rc)
+	rc.Close()
+
+	out, err := imaging.Decode(bytes.NewReader(data))
+	if err != nil {
+		t.Fatalf("decode preview: %v", err)
+	}
+	// 400×300 fits within 1920×1080, so the preview is not downscaled.
+	if b := out.Bounds(); b.Dx() != 400 || b.Dy() != 300 {
+		t.Fatalf("unexpected preview size %v", b.Size())
+	}
+	r, g, b, _ := out.At(200, 150).RGBA()
+	if !(r>>8 > g>>8+40 && r>>8 > b>>8+40) {
+		t.Fatalf("preview is not the source image (r=%d g=%d b=%d)", r>>8, g>>8, b>>8)
+	}
+
+	// The preview cache must be written, and the thumbnail cache must not — they
+	// are separate files served by the same code with different dimensions.
+	if _, err := os.Stat(s.previewCachePath(id)); err != nil {
+		t.Fatalf("preview cache not written: %v", err)
+	}
+	if _, err := os.Stat(s.thumbCachePath(id)); err == nil {
+		t.Fatal("thumbnail cache should not exist after a preview-only request")
+	}
+}

backend/migrations/001_init_schemas.sql

@@ -0,0 +1,65 @@
+-- +goose Up
+
+CREATE EXTENSION IF NOT EXISTS pgcrypto;
+CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
+
+CREATE SCHEMA IF NOT EXISTS core;
+CREATE SCHEMA IF NOT EXISTS data;
+CREATE SCHEMA IF NOT EXISTS acl;
+CREATE SCHEMA IF NOT EXISTS activity;
+
+-- UUID v7 generator
+-- +goose StatementBegin
+CREATE OR REPLACE FUNCTION public.uuid_v7(cts timestamptz DEFAULT clock_timestamp())
+RETURNS uuid LANGUAGE plpgsql AS $$
+DECLARE
+    state text = current_setting('uuidv7.old_tp', true);
+    old_tp text = split_part(state, ':', 1);
+    base int = coalesce(nullif(split_part(state, ':', 4), '')::int, (random()*16777215/2-1)::int);
+    tp text;
+    entropy text;
+    seq text = base;
+    seqn int = split_part(state, ':', 2);
+    ver text = coalesce(split_part(state, ':', 3), to_hex(8+(random()*3)::int));
+BEGIN
+    base = (random()*16777215/2-1)::int;
+    tp = lpad(to_hex(floor(extract(epoch from cts)*1000)::int8), 12, '0') || '7';
+    IF tp IS DISTINCT FROM old_tp THEN
+        old_tp = tp;
+        ver = to_hex(8+(random()*3)::int);
+        base = (random()*16777215/2-1)::int;
+        seqn = base;
+    ELSE
+        seqn = seqn + (random()*1000)::int;
+    END IF;
+    PERFORM set_config('uuidv7.old_tp', old_tp||':'||seqn||':'||ver||':'||base, false);
+    entropy = md5(gen_random_uuid()::text);
+    seq = lpad(to_hex(seqn), 6, '0');
+    RETURN (tp || substring(seq from 1 for 3) || ver || substring(seq from 4 for 3) ||
+            substring(entropy from 1 for 12))::uuid;
+END;
+$$;
+-- +goose StatementEnd
+
+-- Extract timestamp from UUID v7
+-- +goose StatementBegin
+CREATE OR REPLACE FUNCTION public.uuid_extract_timestamp(uuid_val uuid)
+RETURNS timestamptz LANGUAGE sql IMMUTABLE PARALLEL SAFE AS $$
+    SELECT to_timestamp(
+        ('x' || left(replace(uuid_val::text, '-', ''), 12))::bit(48)::bigint / 1000.0
+    );
+$$;
+-- +goose StatementEnd
+
+-- +goose Down
+
+DROP FUNCTION IF EXISTS public.uuid_extract_timestamp(uuid);
+DROP FUNCTION IF EXISTS public.uuid_v7(timestamptz);
+
+DROP SCHEMA IF EXISTS activity;
+DROP SCHEMA IF EXISTS acl;
+DROP SCHEMA IF EXISTS data;
+DROP SCHEMA IF EXISTS core;
+
+DROP EXTENSION IF EXISTS "uuid-ossp";
+DROP EXTENSION IF EXISTS pgcrypto;

backend/migrations/002_core_tables.sql

@@ -0,0 +1,37 @@
+-- +goose Up
+
+CREATE TABLE core.users (
+    id         smallint    GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    name       varchar(32) NOT NULL,
+    password   text        NOT NULL,  -- bcrypt hash via pgcrypto
+    is_admin   boolean     NOT NULL DEFAULT false,
+    can_create boolean     NOT NULL DEFAULT false,
+    is_blocked boolean     NOT NULL DEFAULT false,
+
+    CONSTRAINT uni__users__name UNIQUE (name)
+);
+
+CREATE TABLE core.mime_types (
+    id        smallint     GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    name      varchar(127) NOT NULL,
+    extension varchar(16)  NOT NULL,
+
+    CONSTRAINT uni__mime_types__name UNIQUE (name)
+);
+
+CREATE TABLE core.object_types (
+    id   smallint    GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    name varchar(32) NOT NULL,
+
+    CONSTRAINT uni__object_types__name UNIQUE (name)
+);
+
+COMMENT ON TABLE core.users       IS 'Application users';
+COMMENT ON TABLE core.mime_types  IS 'Whitelist of supported MIME types';
+COMMENT ON TABLE core.object_types IS 'Reference: entity types for ACL and audit log';
+
+-- +goose Down
+
+DROP TABLE IF EXISTS core.object_types;
+DROP TABLE IF EXISTS core.mime_types;
+DROP TABLE IF EXISTS core.users;

backend/migrations/003_data_tables.sql

@@ -0,0 +1,118 @@
+-- +goose Up
+
+CREATE TABLE data.categories (
+    id         uuid         NOT NULL DEFAULT public.uuid_v7() PRIMARY KEY,
+    name       varchar(256) NOT NULL,
+    notes      text,
+    color      char(6),
+    metadata   jsonb,
+    creator_id smallint     NOT NULL REFERENCES core.users(id)
+                            ON UPDATE CASCADE ON DELETE RESTRICT,
+    is_public  boolean      NOT NULL DEFAULT false,
+
+    CONSTRAINT uni__categories__name UNIQUE (name),
+    CONSTRAINT chk__categories__color_hex
+        CHECK (color IS NULL OR color ~* '^[A-Fa-f0-9]{6}$')
+);
+
+CREATE TABLE data.tags (
+    id          uuid         NOT NULL DEFAULT public.uuid_v7() PRIMARY KEY,
+    name        varchar(256) NOT NULL,
+    notes       text,
+    color       char(6),
+    category_id uuid         REFERENCES data.categories(id)
+                             ON UPDATE CASCADE ON DELETE SET NULL,
+    metadata    jsonb,
+    creator_id  smallint     NOT NULL REFERENCES core.users(id)
+                             ON UPDATE CASCADE ON DELETE RESTRICT,
+    is_public   boolean      NOT NULL DEFAULT false,
+
+    CONSTRAINT uni__tags__name UNIQUE (name),
+    CONSTRAINT chk__tags__color_hex
+        CHECK (color IS NULL OR color ~* '^[A-Fa-f0-9]{6}$')
+);
+
+CREATE TABLE data.tag_rules (
+    when_tag_id uuid    NOT NULL REFERENCES data.tags(id)
+                        ON UPDATE CASCADE ON DELETE CASCADE,
+    then_tag_id uuid    NOT NULL REFERENCES data.tags(id)
+                        ON UPDATE CASCADE ON DELETE CASCADE,
+    is_active   boolean NOT NULL DEFAULT true,
+
+    PRIMARY KEY (when_tag_id, then_tag_id)
+);
+
+CREATE TABLE data.files (
+    id               uuid         NOT NULL DEFAULT public.uuid_v7() PRIMARY KEY,
+    original_name    varchar(256),          -- original filename at upload time
+    mime_id          smallint     NOT NULL REFERENCES core.mime_types(id)
+                                  ON UPDATE CASCADE ON DELETE RESTRICT,
+    content_datetime timestamptz  NOT NULL DEFAULT clock_timestamp(),  -- content datetime (e.g. photo taken)
+    notes            text,
+    metadata         jsonb,                 -- user-editable key-value data
+    exif             jsonb,                 -- EXIF data extracted at upload (immutable)
+    phash            bigint,                -- perceptual hash for duplicate detection (future)
+    creator_id       smallint     NOT NULL REFERENCES core.users(id)
+                                  ON UPDATE CASCADE ON DELETE RESTRICT,
+    is_public        boolean      NOT NULL DEFAULT false,
+    is_deleted       boolean      NOT NULL DEFAULT false  -- soft delete (trash)
+);
+
+CREATE TABLE data.file_tag (
+    file_id uuid NOT NULL REFERENCES data.files(id)
+                 ON UPDATE CASCADE ON DELETE CASCADE,
+    tag_id  uuid NOT NULL REFERENCES data.tags(id)
+                 ON UPDATE CASCADE ON DELETE CASCADE,
+
+    PRIMARY KEY (file_id, tag_id)
+);
+
+CREATE TABLE data.pools (
+    id         uuid         NOT NULL DEFAULT public.uuid_v7() PRIMARY KEY,
+    name       varchar(256) NOT NULL,
+    notes      text,
+    metadata   jsonb,
+    creator_id smallint     NOT NULL REFERENCES core.users(id)
+                            ON UPDATE CASCADE ON DELETE RESTRICT,
+    is_public  boolean      NOT NULL DEFAULT false,
+
+    CONSTRAINT uni__pools__name UNIQUE (name)
+);
+
+-- `position` uses integer with gaps (e.g. 1000, 2000, 3000) to allow
+-- insertions without renumbering. Compact when gaps get too small.
+CREATE TABLE data.file_pool (
+    file_id  uuid    NOT NULL REFERENCES data.files(id)
+                     ON UPDATE CASCADE ON DELETE CASCADE,
+    pool_id  uuid    NOT NULL REFERENCES data.pools(id)
+                     ON UPDATE CASCADE ON DELETE CASCADE,
+    position integer NOT NULL DEFAULT 0,
+
+    PRIMARY KEY (file_id, pool_id)
+);
+
+COMMENT ON TABLE  data.categories IS 'Logical grouping of tags';
+COMMENT ON TABLE  data.tags       IS 'File labels/tags';
+COMMENT ON TABLE  data.tag_rules  IS 'Auto-tagging rules: when when_tag is assigned, then_tag follows';
+COMMENT ON TABLE  data.files      IS 'Managed files; actual content stored on disk as {id}.{ext}';
+COMMENT ON TABLE  data.file_tag   IS 'Many-to-many: files <-> tags';
+COMMENT ON TABLE  data.pools      IS 'Ordered collections of files';
+COMMENT ON TABLE  data.file_pool  IS 'Many-to-many: files <-> pools, with ordering';
+
+COMMENT ON COLUMN data.files.original_name    IS 'Original filename at upload time';
+COMMENT ON COLUMN data.files.content_datetime IS 'Content datetime (e.g. when photo was taken); falls back to EXIF DateTimeOriginal';
+COMMENT ON COLUMN data.files.metadata         IS 'User-editable key-value metadata';
+COMMENT ON COLUMN data.files.exif             IS 'EXIF data extracted at upload time (immutable, system-managed)';
+COMMENT ON COLUMN data.files.phash            IS 'Perceptual hash for image/video duplicate detection';
+COMMENT ON COLUMN data.files.is_deleted       IS 'Soft-deleted files (trash); true = in recycle bin';
+COMMENT ON COLUMN data.file_pool.position     IS 'Manual ordering within pool; uses gapped integers';
+
+-- +goose Down
+
+DROP TABLE IF EXISTS data.file_pool;
+DROP TABLE IF EXISTS data.pools;
+DROP TABLE IF EXISTS data.file_tag;
+DROP TABLE IF EXISTS data.files;
+DROP TABLE IF EXISTS data.tag_rules;
+DROP TABLE IF EXISTS data.tags;
+DROP TABLE IF EXISTS data.categories;

backend/migrations/004_acl_tables.sql

@@ -0,0 +1,22 @@
+-- +goose Up
+
+-- If is_public=true on the object, it is accessible to everyone (ACL ignored).
+-- If is_public=false, only creator and users with can_view=true see it.
+-- Admins bypass all ACL checks.
+CREATE TABLE acl.permissions (
+    user_id        smallint NOT NULL REFERENCES core.users(id)
+                            ON UPDATE CASCADE ON DELETE CASCADE,
+    object_type_id smallint NOT NULL REFERENCES core.object_types(id)
+                            ON UPDATE CASCADE ON DELETE RESTRICT,
+    object_id      uuid     NOT NULL,
+    can_view       boolean  NOT NULL DEFAULT true,
+    can_edit       boolean  NOT NULL DEFAULT false,
+
+    PRIMARY KEY (user_id, object_type_id, object_id)
+);
+
+COMMENT ON TABLE acl.permissions IS 'Per-object permissions (used when is_public=false)';
+
+-- +goose Down
+
+DROP TABLE IF EXISTS acl.permissions;

backend/migrations/005_activity_tables.sql

@@ -0,0 +1,82 @@
+-- +goose Up
+
+CREATE TABLE activity.action_types (
+    id   smallint    GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    name varchar(64) NOT NULL,
+
+    CONSTRAINT uni__action_types__name UNIQUE (name)
+);
+
+CREATE TABLE activity.sessions (
+    id            integer      GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    token_hash    text         NOT NULL,  -- hashed session token
+    user_id       smallint     NOT NULL REFERENCES core.users(id)
+                               ON UPDATE CASCADE ON DELETE CASCADE,
+    user_agent    varchar(256) NOT NULL,
+    started_at    timestamptz  NOT NULL DEFAULT statement_timestamp(),
+    expires_at    timestamptz,
+    last_activity timestamptz  NOT NULL DEFAULT statement_timestamp(),
+    is_active     boolean      NOT NULL DEFAULT true,
+
+    CONSTRAINT uni__sessions__token_hash UNIQUE (token_hash)
+);
+
+CREATE TABLE activity.file_views (
+    file_id    uuid        NOT NULL REFERENCES data.files(id)
+                           ON UPDATE CASCADE ON DELETE CASCADE,
+    user_id    smallint    NOT NULL REFERENCES core.users(id)
+                           ON UPDATE CASCADE ON DELETE CASCADE,
+    viewed_at  timestamptz NOT NULL DEFAULT statement_timestamp(),
+
+    PRIMARY KEY (file_id, viewed_at, user_id)
+);
+
+CREATE TABLE activity.pool_views (
+    pool_id    uuid        NOT NULL REFERENCES data.pools(id)
+                           ON UPDATE CASCADE ON DELETE CASCADE,
+    user_id    smallint    NOT NULL REFERENCES core.users(id)
+                           ON UPDATE CASCADE ON DELETE CASCADE,
+    viewed_at  timestamptz NOT NULL DEFAULT statement_timestamp(),
+
+    PRIMARY KEY (pool_id, viewed_at, user_id)
+);
+
+CREATE TABLE activity.tag_uses (
+    tag_id      uuid        NOT NULL REFERENCES data.tags(id)
+                            ON UPDATE CASCADE ON DELETE CASCADE,
+    user_id     smallint    NOT NULL REFERENCES core.users(id)
+                            ON UPDATE CASCADE ON DELETE CASCADE,
+    used_at     timestamptz NOT NULL DEFAULT statement_timestamp(),
+    is_included boolean     NOT NULL,  -- true=included in filter, false=excluded
+
+    PRIMARY KEY (tag_id, used_at, user_id)
+);
+
+CREATE TABLE activity.audit_log (
+    id             bigint      GENERATED ALWAYS AS IDENTITY PRIMARY KEY,
+    user_id        smallint    NOT NULL REFERENCES core.users(id)
+                               ON UPDATE CASCADE ON DELETE RESTRICT,
+    action_type_id smallint    NOT NULL REFERENCES activity.action_types(id)
+                               ON UPDATE CASCADE ON DELETE RESTRICT,
+    object_type_id smallint    REFERENCES core.object_types(id)
+                               ON UPDATE CASCADE ON DELETE RESTRICT,
+    object_id      uuid,
+    details        jsonb,               -- action-specific payload
+    performed_at   timestamptz NOT NULL DEFAULT statement_timestamp()
+);
+
+COMMENT ON TABLE activity.action_types IS 'Reference: types of auditable user actions';
+COMMENT ON TABLE activity.sessions     IS 'Active user sessions';
+COMMENT ON TABLE activity.file_views   IS 'File view history';
+COMMENT ON TABLE activity.pool_views   IS 'Pool view history';
+COMMENT ON TABLE activity.tag_uses     IS 'Tag usage in filters';
+COMMENT ON TABLE activity.audit_log    IS 'Unified audit trail for all user actions';
+
+-- +goose Down
+
+DROP TABLE IF EXISTS activity.audit_log;
+DROP TABLE IF EXISTS activity.tag_uses;
+DROP TABLE IF EXISTS activity.pool_views;
+DROP TABLE IF EXISTS activity.file_views;
+DROP TABLE IF EXISTS activity.sessions;
+DROP TABLE IF EXISTS activity.action_types;

backend/migrations/006_indexes.sql

@@ -0,0 +1,87 @@
+-- +goose Up
+
+-- core
+CREATE INDEX idx__users__name ON core.users USING hash (name);
+
+-- data.categories
+CREATE INDEX idx__categories__creator_id ON data.categories USING hash (creator_id);
+
+-- data.tags
+CREATE INDEX idx__tags__category_id ON data.tags USING hash (category_id);
+CREATE INDEX idx__tags__creator_id  ON data.tags USING hash (creator_id);
+
+-- data.tag_rules
+CREATE INDEX idx__tag_rules__when ON data.tag_rules USING hash (when_tag_id);
+CREATE INDEX idx__tag_rules__then ON data.tag_rules USING hash (then_tag_id);
+
+-- data.files
+CREATE INDEX idx__files__mime_id           ON data.files USING hash (mime_id);
+CREATE INDEX idx__files__creator_id        ON data.files USING hash (creator_id);
+CREATE INDEX idx__files__content_datetime  ON data.files USING btree (content_datetime DESC NULLS LAST);
+CREATE INDEX idx__files__is_deleted        ON data.files USING btree (is_deleted) WHERE is_deleted = true;
+CREATE INDEX idx__files__phash             ON data.files USING btree (phash) WHERE phash IS NOT NULL;
+
+-- data.file_tag
+CREATE INDEX idx__file_tag__tag_id  ON data.file_tag USING hash (tag_id);
+CREATE INDEX idx__file_tag__file_id ON data.file_tag USING hash (file_id);
+
+-- data.pools
+CREATE INDEX idx__pools__creator_id ON data.pools USING hash (creator_id);
+
+-- data.file_pool
+CREATE INDEX idx__file_pool__pool_id ON data.file_pool USING hash (pool_id);
+CREATE INDEX idx__file_pool__file_id ON data.file_pool USING hash (file_id);
+
+-- acl.permissions
+CREATE INDEX idx__acl__object ON acl.permissions USING btree (object_type_id, object_id);
+CREATE INDEX idx__acl__user   ON acl.permissions USING hash (user_id);
+
+-- activity.sessions
+CREATE INDEX idx__sessions__user_id    ON activity.sessions USING hash (user_id);
+CREATE INDEX idx__sessions__token_hash ON activity.sessions USING hash (token_hash);
+
+-- activity.file_views
+CREATE INDEX idx__file_views__user_id ON activity.file_views USING hash (user_id);
+
+-- activity.pool_views
+CREATE INDEX idx__pool_views__user_id ON activity.pool_views USING hash (user_id);
+
+-- activity.tag_uses
+CREATE INDEX idx__tag_uses__user_id ON activity.tag_uses USING hash (user_id);
+
+-- activity.audit_log
+CREATE INDEX idx__audit_log__user_id        ON activity.audit_log USING hash (user_id);
+CREATE INDEX idx__audit_log__action_type_id ON activity.audit_log USING hash (action_type_id);
+CREATE INDEX idx__audit_log__object         ON activity.audit_log USING btree (object_type_id, object_id)
+    WHERE object_id IS NOT NULL;
+CREATE INDEX idx__audit_log__performed_at   ON activity.audit_log USING btree (performed_at DESC);
+
+-- +goose Down
+
+DROP INDEX IF EXISTS activity.idx__audit_log__performed_at;
+DROP INDEX IF EXISTS activity.idx__audit_log__object;
+DROP INDEX IF EXISTS activity.idx__audit_log__action_type_id;
+DROP INDEX IF EXISTS activity.idx__audit_log__user_id;
+DROP INDEX IF EXISTS activity.idx__tag_uses__user_id;
+DROP INDEX IF EXISTS activity.idx__pool_views__user_id;
+DROP INDEX IF EXISTS activity.idx__file_views__user_id;
+DROP INDEX IF EXISTS activity.idx__sessions__token_hash;
+DROP INDEX IF EXISTS activity.idx__sessions__user_id;
+DROP INDEX IF EXISTS acl.idx__acl__user;
+DROP INDEX IF EXISTS acl.idx__acl__object;
+DROP INDEX IF EXISTS data.idx__file_pool__file_id;
+DROP INDEX IF EXISTS data.idx__file_pool__pool_id;
+DROP INDEX IF EXISTS data.idx__pools__creator_id;
+DROP INDEX IF EXISTS data.idx__file_tag__file_id;
+DROP INDEX IF EXISTS data.idx__file_tag__tag_id;
+DROP INDEX IF EXISTS data.idx__files__phash;
+DROP INDEX IF EXISTS data.idx__files__is_deleted;
+DROP INDEX IF EXISTS data.idx__files__content_datetime;
+DROP INDEX IF EXISTS data.idx__files__creator_id;
+DROP INDEX IF EXISTS data.idx__files__mime_id;
+DROP INDEX IF EXISTS data.idx__tag_rules__then;
+DROP INDEX IF EXISTS data.idx__tag_rules__when;
+DROP INDEX IF EXISTS data.idx__tags__creator_id;
+DROP INDEX IF EXISTS data.idx__tags__category_id;
+DROP INDEX IF EXISTS data.idx__categories__creator_id;
+DROP INDEX IF EXISTS core.idx__users__name;

backend/migrations/007_seed_data.sql

@@ -0,0 +1,49 @@
+-- +goose Up
+
+INSERT INTO core.mime_types (name, extension) VALUES
+    ('image/jpeg',       'jpg'),
+    ('image/png',        'png'),
+    ('image/gif',        'gif'),
+    ('image/webp',       'webp'),
+    ('video/mp4',        'mp4'),
+    ('video/quicktime',  'mov'),
+    ('video/x-msvideo',  'avi'),
+    ('video/webm',       'webm'),
+    ('video/3gpp',       '3gp'),
+    ('video/x-m4v',      'm4v');
+
+INSERT INTO core.object_types (name) VALUES
+    ('file'), ('tag'), ('category'), ('pool');
+
+INSERT INTO activity.action_types (name) VALUES
+    -- Auth
+    ('user_login'), ('user_logout'),
+    -- Files
+    ('file_create'), ('file_edit'), ('file_delete'), ('file_restore'),
+    ('file_permanent_delete'), ('file_replace'),
+    -- Tags
+    ('tag_create'), ('tag_edit'), ('tag_delete'),
+    -- Categories
+    ('category_create'), ('category_edit'), ('category_delete'),
+    -- Pools
+    ('pool_create'), ('pool_edit'), ('pool_delete'),
+    -- Relations
+    ('file_tag_add'), ('file_tag_remove'),
+    ('file_pool_add'), ('file_pool_remove'),
+    -- ACL
+    ('acl_change'),
+    -- Admin
+    ('user_create'), ('user_delete'), ('user_block'), ('user_unblock'),
+    ('user_role_change'),
+    -- Sessions
+    ('session_terminate');
+
+-- The initial administrator is created at application startup from the
+-- ADMIN_USERNAME / ADMIN_PASSWORD environment variables (see UserService.
+-- EnsureAdmin), so no default credentials are seeded here.
+
+-- +goose Down
+
+DELETE FROM activity.action_types;
+DELETE FROM core.object_types;
+DELETE FROM core.mime_types;

backend/migrations/embed.go

@@ -0,0 +1,8 @@
+package migrations
+
+import "embed"
+
+// FS holds all goose migration SQL files, embedded at build time.
+//
+//go:embed *.sql
+var FS embed.FS

bot/tfm-tb.py

@@ -1,170 +0,0 @@
-#!../venv/bin/python3
-
-import telebot
-import sys
-import os
-import atexit
-import signal
-from time import sleep
-from socket import getaddrinfo
-from requests import get
-from subprocess import check_output
-import logging as log
-from json import loads as ljson
-from datetime import datetime
-import pytz
-
-sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__))))
-import api.tfm_api as tfm_api
-
-# set logger
-log.basicConfig(
-	level=log.INFO,
-	filename="/var/log/tfm/tfm-tb.log",
-	filemode="a",
-	format="%(asctime)s | %(threadName)s | %(levelname)s | %(message)s"
-)
-
-# actions to do on exit
-exit_actions = []
-defer = exit_actions.append
-def finalize(*args):
-	exec('\n'.join(exit_actions))
-	os._exit(0)
-atexit.register(finalize)
-signal.signal(signal.SIGTERM, finalize)
-signal.signal(signal.SIGINT, finalize)
-
-# initialize TFM API
-try:
-	tfm_api.Initialize()
-	tfm = tfm_api.TSession("af6dde9b-7be1-46f2-872e-9a06ce3d3358")
-except Exception as e:
-	log.critical(f"failed to initialize TFM API: {str(e)}")
-	exit(1)
-
-# initialize bot
-tfm_tb = telebot.TeleBot(tfm_api.conf["Telebot"]["Token"])
-
-TZ = pytz.timezone("Europe/Moscow")
-
-
-# check if user is authorized and if chat exists in db
-def check_chat(message):
-	return message.from_user.id == 924090228
-
-
-# file handler
-@tfm_tb.message_handler(content_types=['document', 'photo', 'audio', 'video', 'voice', 'animation'])
-def file_handler(message):
-	if not check_chat(message):
-		return
-	notes = None
-	orig_name = None
-	if message.forward_from_chat:
-		notes = f"Telegram origin: \"{message.forward_from_chat.title}\" ({message.forward_from_chat.username})"
-	if message.photo:
-		fname = f"{message.photo[-1].file_unique_id}"
-		log.info(f"got photo '{fname}'")
-		file_info = tfm_tb.get_file(message.photo[-1].file_id)
-		file_path = os.path.join(tfm_api.conf["Telebot"]["SaveFolder"], fname)
-		with open(file_path, 'wb') as f:
-			f.write(tfm_tb.download_file(file_info.file_path))
-	elif message.video:
-		fname = f"{message.video.file_unique_id}"
-		log.info(f"got video '{fname}'")
-		file_info = tfm_tb.get_file(message.video.file_id)
-		file_path = os.path.join(tfm_api.conf["Telebot"]["SaveFolder"], fname)
-		with open(file_path, 'wb') as f:
-			f.write(tfm_tb.download_file(file_info.file_path))
-	else:
-		file = None
-		if message.document:
-			file = message.document
-		elif message.animation:
-			file = message.animation
-		else:
-			tfm_tb.reply_to(message, "Unsupported file type.")
-			return
-		log.info(f"got file '{file.file_name}'")
-		orig_name = file.file_name
-		file_info = tfm_tb.get_file(file.file_id)
-		file_path = os.path.join(tfm_api.conf["Telebot"]["SaveFolder"], f"{file.file_unique_id}")
-	try:
-		with open(file_path, 'wb') as f:
-			f.write(tfm_tb.download_file(file_info.file_path))
-		log.info(f"downloaded file '{file_path}'")
-		exif = ljson(os.popen(f"exiftool -json \"{file_path}\"").read())[0]
-		dt = exif["FileModifyDate"]
-		if "SubSecCreateDate" in exif.keys():
-			dt = exif["SubSecCreateDate"]
-		if '.' in dt:
-			dt = datetime.strptime(dt, "%Y:%m:%d %H:%M:%S.%f%z")
-		else:
-			dt = datetime.strptime(dt, "%Y:%m:%d %H:%M:%S%z")
-		file_id, ext = tfm.add_file(file_path, dt, notes, orig_name=orig_name)
-		tfm.add_file_to_tag(file_id, "d6d8129a-984d-4451-8c83-d04523ced8a8")
-	except Exception as e:
-		tfm_tb.reply_to(message, "Error: %s" % str(e).split('\n')[0])
-		log.info(f"Error: %s" % str(e).split('\n')[0])
-		os.remove(file_path)
-		log.info(f"removed file '{file_path}'")
-	else:
-		tfm_tb.reply_to(message, "File saved.")
-		log.info(f"imported file '{file_path}'")
-
-
-# folder scanner
-@tfm_tb.message_handler(commands=['scan'])
-def scan(message):
-	tfm_tb.reply_to(message, "Scanning...")
-	log.info("Scanning...")
-	scan_dir = "/srv/hfs/misc/tfm_temp/scan"
-	files = []
-	for file in os.listdir(scan_dir):
-		new_file = {"name": file}
-		file = os.path.join(scan_dir, file)
-		if not os.path.isfile(file):
-			continue
-		new_file["path"] = file
-		exif = ljson(os.popen(f"exiftool -json \"{file}\"").read())[0]
-		dt = exif["FileModifyDate"]
-		if "SubSecDateTimeOriginal" in exif.keys():
-			dt = exif["SubSecDateTimeOriginal"]
-		elif "DateTimeOriginal" in exif.keys():
-			dt = exif["DateTimeOriginal"]
-		if '.' in dt:
-			try:
-				dt = datetime.strptime(dt, "%Y:%m:%d %H:%M:%S.%f%z")
-			except:
-				dt = TZ.localize(datetime.strptime(dt, "%Y:%m:%d %H:%M:%S.%f"))
-		else:
-			try:
-				dt = datetime.strptime(dt, "%Y:%m:%d %H:%M:%S%z")
-			except:
-				dt = TZ.localize(datetime.strptime(dt, "%Y:%m:%d %H:%M:%S"))
-		new_file["datetime"] = dt
-		files.append(new_file)
-	tfm_tb.reply_to(message, f"{len(files)} files found.")
-	log.info(f"{len(files)} files found.")
-	files.sort(key=lambda f: f["datetime"])
-	for file in files:
-		try:
-			file_id, ext = tfm.add_file(file["path"], file["datetime"])
-			tfm.add_file_to_tag(file_id, "d6d8129a-984d-4451-8c83-d04523ced8a8")
-		except Exception as e:
-			tfm_tb.reply_to(message, f"Error adding file '{file['name']}': {str(e)}")
-			log.error(f"Error adding file '{file['name']}': {str(e)}")
-	tfm_tb.reply_to(message, "Files added.")
-	log.info("Files added.")
-
-
-if __name__ == '__main__':
-	log.info("tfm-tb started")
-	defer("log.info(\"tfm-tb stopped\")")
-	while True:
-		try:
-			tfm_tb.polling(none_stop=True)
-		except Exception as e:
-			log.exception("exception on polling")
-			sleep(1)

docker-compose.yml

@@ -0,0 +1,104 @@
+# =============================================================================
+# Tanabata File Manager — Docker Compose
+#
+# Quick start:
+#   cp .env.example .env        # then edit the secrets
+#   docker compose up -d --build
+#
+# Database — two supported modes, selected in .env:
+#
+#   1. Bundled Postgres container (default).
+#        COMPOSE_PROFILES=with-db
+#        DATABASE_URL=postgres://tanabata:password@db:5432/tanabata?sslmode=disable
+#
+#   2. Postgres already running on the host.
+#        COMPOSE_PROFILES=          # empty → the db container is not started
+#        DATABASE_URL=postgres://tanabata:password@host.docker.internal:5432/tanabata?sslmode=disable
+#
+# Requires Docker Compose v2.20+ (for depends_on.required).
+# =============================================================================
+
+services:
+  app:
+    build:
+      context: .
+      dockerfile: Dockerfile
+    container_name: tfm
+    restart: unless-stopped
+
+    # All application config (secrets, DATABASE_URL, tunables) comes from .env.
+    env_file: .env
+
+    # Pin STATIC_DIR to the path baked into the image. .env intentionally leaves
+    # it unset; pinning here guarantees in-container SPA serving can't be
+    # disabled by an empty value leaking in through env_file.
+    environment:
+      STATIC_DIR: /app/static
+
+    # The container always listens on 42776 (Dockerfile default); APP_PORT only
+    # changes the host-published port.
+    ports:
+      - "${APP_PORT:-42776}:42776"
+
+    # Wait for the bundled DB when the with-db profile is active. When using a
+    # host Postgres the db service is disabled, and required:false keeps this
+    # dependency from erroring or auto-starting it.
+    depends_on:
+      db:
+        condition: service_healthy
+        required: false
+
+    # Lets DATABASE_URL reach a Postgres on the host via host.docker.internal
+    # (needed on Linux; harmless elsewhere).
+    extra_hosts:
+      - "host.docker.internal:host-gateway"
+
+    # Run as this uid:gid. Relevant when the mounts below are bind-mounted to
+    # host folders: set PUID/PGID (in .env) to the owner of those folders so the
+    # container can write to them. Defaults to the image's tanabata user
+    # (42776), which owns the named volumes.
+    user: "${PUID:-42776}:${PGID:-42776}"
+
+    # Storage for originals, the thumbnail cache, and the import drop folder.
+    # Each source defaults to a named volume but can be pointed at a specific
+    # host folder via FILES_DIR / THUMBS_DIR / IMPORT_DIR in .env (a path turns
+    # the mount into a host bind mount; a bare name stays a named volume).
+    volumes:
+      - "${FILES_DIR:-app_files}:/data/files"
+      - "${THUMBS_DIR:-app_thumbs}:/data/thumbs"
+      - "${IMPORT_DIR:-app_import}:/data/import"
+
+  db:
+    image: postgres:14-alpine
+    restart: unless-stopped
+
+    # Only started when COMPOSE_PROFILES includes "with-db". Disable it to point
+    # the app at a Postgres running on the host instead.
+    profiles: ["with-db"]
+
+    environment:
+      POSTGRES_DB: ${POSTGRES_DB:-tanabata}
+      POSTGRES_USER: ${POSTGRES_USER:-tanabata}
+      POSTGRES_PASSWORD: ${POSTGRES_PASSWORD:-password}
+
+    # Defaults to a named volume; set DB_DIR in .env to a host folder to bind
+    # mount it instead. Postgres fixes the folder's ownership itself, so DB_DIR
+    # needs no PUID/PGID.
+    volumes:
+      - "${DB_DIR:-db_data}:/var/lib/postgresql/data"
+
+    # Uncomment to reach the DB from the host (e.g. with psql) for debugging.
+    # ports:
+    #   - "5432:5432"
+
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U ${POSTGRES_USER:-tanabata} -d ${POSTGRES_DB:-tanabata}"]
+      interval: 5s
+      timeout: 5s
+      retries: 10
+
+volumes:
+  app_files:
+  app_thumbs:
+  app_import:
+  db_data:

docs/DEPLOY.md

@@ -0,0 +1,182 @@
+# Deployment (Gitea Actions → host)
+
+Tanabata is deployed by a [Gitea Actions](https://docs.gitea.com/usage/actions/overview)
+workflow ([`.gitea/workflows/deploy.yml`](../.gitea/workflows/deploy.yml)) that
+runs on the **production host itself**. On every push to `master` it updates the
+git clone in `/opt/tanabata` and runs `docker compose up -d --build` there, so the
+image is built from the freshly-pushed code and the stack is restarted.
+
+```
+push master ──> Gitea (container) ──> act_runner (host, "host" label)
+                                          │ git fetch + reset --hard   (in /opt/tanabata)
+                                          └ docker compose up -d --build
+```
+
+The Gitea server runs in a container, but the **runner runs directly on the host**
+(shell executor) so it can use the host's git, the host Docker daemon, and the
+clone in `/opt/tanabata`. Nothing needs a registry — the host builds the image
+locally. The workflow uses only shell steps, so the host needs just **git** and
+**docker** (no node, no rsync).
+
+## What is a runner?
+
+Gitea (like GitHub) only *coordinates* CI: it stores the workflow, queues jobs,
+and shows logs. It does **not** execute anything itself. A **runner** is a
+separate agent program that polls Gitea for queued jobs, runs the steps on a
+machine you control, and reports results back.
+
+Gitea's official runner is **act_runner** (a single Go binary; it uses the
+`act` engine to interpret workflow YAML). One act_runner process can serve many
+repos. Each runner advertises one or more **labels**, and a job's `runs-on:`
+picks a runner by label. A label also decides *how* a job runs — the **executor**:
+
+- **docker executor** — each job runs in a fresh container from an image (e.g.
+  `node:20-bookworm`). Isolated and reproducible; the usual default. Label form
+  at registration: `ubuntu:docker://node:20-bookworm`.
+- **host / shell executor** — the job runs directly on the host as the runner's
+  user, using host-installed tools. Label form: `host:host`. This is what we use,
+  because the deploy needs the host's Docker daemon and `/opt/tanabata`.
+
+So `runs-on: host` in the workflow ⇒ "run this job on a runner that registered a
+`host` label" ⇒ our shell executor on the prod box.
+
+## One-time setup
+
+### 1. Enable Actions in Gitea
+
+Gitea 1.21+ has Actions on by default. Otherwise add to `app.ini` and restart:
+
+```ini
+[actions]
+ENABLED = true
+```
+
+### 2. A runner user on the host
+
+Pick (or create) the Linux user the runner runs as. It must be able to use Docker
+and own the deploy dir — so the workflow needs no `sudo`:
+
+```bash
+sudo useradd -r -m -d /home/gitea-runner gitea-runner   # or reuse an existing user
+sudo usermod -aG docker gitea-runner                     # host Docker access
+```
+
+The host needs `git` and a Docker engine with the Compose plugin:
+
+```bash
+sudo apt install -y git docker.io docker-compose-plugin   # Debian/Ubuntu
+```
+
+### 3. Clone the repo to /opt/tanabata once
+
+The workflow only does `git fetch` + `reset --hard`, so the clone (and its auth)
+is established here, once. Use a **read-only deploy key** so the host never holds
+write credentials:
+
+```bash
+# As the runner user, create a key and add the PUBLIC half to the repo in Gitea:
+#   Repo → Settings → Deploy Keys → Add (read-only)
+sudo -u gitea-runner ssh-keygen -t ed25519 -f /home/gitea-runner/.ssh/tanabata_deploy -N ''
+
+# Clone with that key (SSH URL of your Gitea repo):
+sudo -u gitea-runner GIT_SSH_COMMAND='ssh -i /home/gitea-runner/.ssh/tanabata_deploy' \
+  git clone git@gitea.example.com:you/tanabata.git /opt/tanabata
+sudo chown -R gitea-runner:gitea-runner /opt/tanabata
+```
+
+> HTTPS works too — clone with a URL that carries a read-only token. SSH deploy
+> keys are the cleaner, per-repo, read-only option.
+
+After cloning, recurring `git fetch` reuses the remote + key stored in
+`/opt/tanabata/.git/config`, so the runner itself needs no standing credentials.
+
+### 4. Register and run act_runner on the host
+
+Get a registration token in Gitea. **Where you create it sets the runner's
+scope** (and `--name` is only a display label, unrelated to scope):
+
+- **Repository** (Tanabata repo → Settings → Actions → Runners) → serves only
+  this repo. **Use this.**
+- Organization → all repos in the org; Site (admin) → all repos on the instance.
+
+> Security: this runner is a host/shell executor with access to the Docker
+> socket — effectively root on the host. Register it at the **repository** level
+> so only Tanabata's workflows can run on your prod server; a site-wide runner
+> would let any repo's workflow execute arbitrary commands here.
+
+Then, as the runner user:
+
+```bash
+# Download act_runner: https://gitea.com/gitea/act_runner/releases
+act_runner register --no-interactive \
+  --instance https://gitea.example.com \
+  --token   <REGISTRATION_TOKEN> \
+  --name    prod-host \
+  --labels  host:host          # <-- maps `runs-on: host` to the shell executor
+
+# Run it (use a systemd unit in production so it survives reboots):
+act_runner daemon
+```
+
+`--labels host:host` is what makes jobs run **on the host** instead of in a
+container. The instance URL must be reachable from the host (Gitea's published
+port / domain — not the in-container address). Registration writes a `.runner`
+file (the runner's credentials) in the working directory.
+
+Minimal systemd unit (`/etc/systemd/system/act_runner.service`):
+
+```ini
+[Unit]
+Description=Gitea act_runner
+After=docker.service
+Requires=docker.service
+
+[Service]
+User=gitea-runner
+WorkingDirectory=/home/gitea-runner
+ExecStart=/usr/local/bin/act_runner daemon
+Restart=always
+
+[Install]
+WantedBy=multi-user.target
+```
+
+```bash
+sudo systemctl enable --now act_runner
+```
+
+### 5. Create /opt/tanabata/.env (secrets)
+
+The workflow **never** writes `.env` — it lives on the host and holds the real
+secrets and the chosen DB mode. `.env` is git-ignored, so `git reset --hard`
+leaves it untouched. Create it once:
+
+```bash
+cd /opt/tanabata
+sudo -u gitea-runner cp .env.example .env
+sudo -u gitea-runner $EDITOR .env    # set JWT_SECRET, ADMIN_PASSWORD, DATABASE_URL, etc.
+```
+
+See [`.env.example`](../.env.example) for every variable. For the bundled
+Postgres keep `COMPOSE_PROFILES=with-db`; to use a Postgres already on the host,
+set it empty and point `DATABASE_URL` at `host.docker.internal`.
+
+> Data lives in named Docker volumes by default (or the `*_DIR` host paths you
+> set in `.env`, e.g. `/var/lib/tanabata/...`) — **not** in `/opt/tanabata`. So
+> `git reset --hard` on the code dir never touches your data.
+
+## Deploying
+
+Push to `master` (or hit **Run workflow** on the Actions tab). Watch progress
+under the repo's **Actions** tab. The first build pulls the Node/Go base images
+and takes a few minutes; later builds reuse the host's layer cache.
+
+## Notes / alternatives
+
+- **Docker-executor runner instead of host.** If you'd rather the runner itself
+  run in a container, register with a Docker label and bind-mount
+  `/var/run/docker.sock` and `/opt/tanabata` into the job (act_runner
+  `config.yaml` → `container.valid_volumes`), then change `runs-on` accordingly.
+  The host executor above is simpler for host deploys.
+- **Zero-downtime** isn't attempted: `compose up` recreates changed containers.
+  For a single-node setup the brief restart is usually fine.

docs/FRONTEND_STRUCTURE.md

@@ -0,0 +1,422 @@
+# Tanabata File Manager — Frontend Structure
+
+## Stack
+
+- **Framework**: SvelteKit (SPA mode, `ssr: false`)
+- **Language**: TypeScript
+- **CSS**: Tailwind CSS + CSS custom properties (hybrid)
+- **API types**: Auto-generated via openapi-typescript
+- **PWA**: Service worker + web manifest
+- **Font**: Epilogue (variable weight)
+- **Package manager**: npm
+
+## SPA mode — why SvelteKit without the server
+
+This frontend runs as a **pure client-side SPA**: `adapter-static` with
+`fallback: 'index.html'` and `ssr = false` globally (see
+`src/routes/+layout.ts`). There is no Node server in production — the build is
+static assets, and the only backend is the Go API. SvelteKit is used here
+purely as an SPA framework: file-based routing, the client router, and build
+tooling.
+
+**SvelteKit features we *do* use:**
+
+- File-based routing with nested layouts (`admin/` has its own guard) and
+  dynamic segments (`[id]`).
+- The client router: `goto`, the `page` store/state, `afterNavigate`,
+  `navigating`.
+- **Shallow routing** — `pushState`/`replaceState` + `page.state`. The
+  Immich-style file viewer in `files/` and `pools/[id]/` opens as an overlay
+  over the still-mounted list via shallow routing, so the browser back button
+  dismisses it without reloading the grid. This is the single biggest reason we
+  stay on SvelteKit rather than a plain router.
+- `load` functions, used *only* as client-side route guards (auth redirect,
+  admin redirect, `/` → `/files`).
+- `$lib` alias, generated `./$types`, Vite/HMR integration.
+
+**SvelteKit features we deliberately do *not* use** (the "server half"):
+
+- SSR / hydration.
+- `+page.server.ts`, `+server.ts` endpoints, form actions — all data goes
+  through the Go API via the `$lib/api` client.
+- `hooks.*`, prerendering, server-only modules — no `hooks.server.ts` /
+  `hooks.client.ts` files exist.
+
+**Decision: stay on SvelteKit, do not migrate to a bare Svelte + router SPA.**
+The project already *is* an SPA, so there is no runtime gain from switching
+(adapter-static tree-shakes the unused server bits; the client-runtime size
+difference is negligible). A migration would mean re-implementing nested
+layouts, guards, dynamic params, and — most painfully — shallow routing /
+history-state overlays by hand, for zero benefit. New contributors should not
+expect SSR, endpoints, or hooks to do anything here; that is intentional.
+
+## Monorepo Layout
+
+```
+tanabata/
+├── backend/                    ← Go project (go.mod in here)
+│   ├── cmd/
+│   ├── internal/
+│   ├── migrations/
+│   ├── go.mod
+│   └── go.sum
+│
+├── frontend/                   ← SvelteKit project (package.json in here)
+│   └── (see below)
+│
+├── openapi.yaml                ← Shared API contract (root level)
+├── docker-compose.yml
+├── Dockerfile
+├── .env.example
+└── README.md
+```
+
+`openapi.yaml` lives at repository root — both backend and frontend
+reference it. The frontend generates types from it; the backend
+validates its handlers against it.
+
+## Frontend Directory Layout
+
+```
+frontend/
+├── package.json
+├── svelte.config.js
+├── vite.config.ts
+├── tsconfig.json
+├── tailwind.config.ts
+├── postcss.config.js
+│
+├── src/
+│   ├── app.html                    # Shell HTML (PWA meta, font preload)
+│   ├── app.css                     # Tailwind directives + CSS custom properties
+│   │                               # (no hooks.* — see "SPA mode" above)
+│   │
+│   ├── lib/                        # Shared code ($lib/ alias)
+│   │   │
+│   │   ├── api/                    # API client layer
+│   │   │   ├── client.ts           # Base fetch wrapper: auth headers, token refresh,
+│   │   │   │                       # error parsing, base URL
+│   │   │   ├── files.ts            # listFiles, getFile, uploadFile, deleteFile, etc.
+│   │   │   ├── tags.ts             # listTags, createTag, getTag, updateTag, etc.
+│   │   │   ├── categories.ts       # Category API functions
+│   │   │   ├── pools.ts            # Pool API functions
+│   │   │   ├── auth.ts             # login, logout, refresh, listSessions
+│   │   │   ├── acl.ts              # getPermissions, setPermissions
+│   │   │   ├── users.ts            # getMe, updateMe, admin user CRUD
+│   │   │   ├── audit.ts            # queryAuditLog
+│   │   │   ├── schema.ts           # AUTO-GENERATED from openapi.yaml (do not edit)
+│   │   │   └── types.ts            # Friendly type aliases:
+│   │   │                           #   export type File = components["schemas"]["File"]
+│   │   │                           #   export type Tag = components["schemas"]["Tag"]
+│   │   │
+│   │   ├── components/             # Reusable UI components
+│   │   │   │
+│   │   │   ├── layout/             # App shell
+│   │   │   │   ├── Navbar.svelte       # Bottom navigation bar (mobile-first)
+│   │   │   │   ├── Header.svelte       # Section header with sorting controls
+│   │   │   │   ├── SelectionBar.svelte # Floating bar for multi-select actions
+│   │   │   │   └── Loader.svelte       # Full-screen loading overlay
+│   │   │   │
+│   │   │   ├── file/               # File-related components
+│   │   │   │   ├── FileGrid.svelte     # Thumbnail grid with infinite scroll
+│   │   │   │   ├── FileCard.svelte     # Single thumbnail (160×160, selectable)
+│   │   │   │   ├── FileViewer.svelte   # Full-screen preview with prev/next navigation
+│   │   │   │   ├── FileUpload.svelte   # Upload form + drag-and-drop zone
+│   │   │   │   ├── FileDetail.svelte   # Metadata editor (notes, datetime, tags)
+│   │   │   │   └── FilterBar.svelte    # DSL filter builder UI
+│   │   │   │
+│   │   │   ├── tag/                # Tag-related components
+│   │   │   │   ├── TagBadge.svelte     # Colored pill with tag name
+│   │   │   │   ├── TagPicker.svelte    # Searchable tag selector (add/remove)
+│   │   │   │   ├── TagList.svelte      # Tag grid for section view
+│   │   │   │   └── TagRuleEditor.svelte # Auto-tag rule management
+│   │   │   │
+│   │   │   ├── pool/               # Pool-related components
+│   │   │   │   ├── PoolCard.svelte     # Pool preview card
+│   │   │   │   ├── PoolFileList.svelte # Ordered file list with drag reorder
+│   │   │   │   └── PoolDetail.svelte   # Pool metadata editor
+│   │   │   │
+│   │   │   ├── acl/                # Access control components
+│   │   │   │   └── PermissionEditor.svelte  # User permission grid
+│   │   │   │
+│   │   │   └── common/             # Shared primitives
+│   │   │       ├── Button.svelte
+│   │   │       ├── Modal.svelte
+│   │   │       ├── ConfirmDialog.svelte
+│   │   │       ├── Toast.svelte
+│   │   │       ├── InfiniteScroll.svelte
+│   │   │       ├── Pagination.svelte
+│   │   │       ├── SortDropdown.svelte
+│   │   │       ├── SearchInput.svelte
+│   │   │       ├── ColorPicker.svelte
+│   │   │       ├── Checkbox.svelte     # Three-state: checked, unchecked, partial
+│   │   │       └── EmptyState.svelte
+│   │   │
+│   │   ├── stores/                 # Svelte stores (global state)
+│   │   │   ├── auth.ts             # Current user, JWT tokens, isAuthenticated
+│   │   │   ├── selection.ts        # Selected item IDs, selection mode toggle
+│   │   │   ├── sorting.ts          # Per-section sort key + order (persisted to localStorage)
+│   │   │   ├── theme.ts            # Dark/light mode (persisted, respects prefers-color-scheme)
+│   │   │   └── toast.ts            # Notification queue (success, error, info)
+│   │   │
+│   │   └── utils/                  # Pure helper functions
+│   │       ├── format.ts           # formatDate, formatFileSize, formatDuration
+│   │       ├── dsl.ts              # Filter DSL builder: UI state → query string
+│   │       ├── pwa.ts              # PWA reset, cache clear, update prompt
+│   │       └── keyboard.ts         # Keyboard shortcut helpers (Ctrl+A, Escape, etc.)
+│   │
+│   ├── routes/                     # SvelteKit file-based routing
+│   │   │
+│   │   ├── +layout.svelte          # Root layout: Navbar, theme wrapper, toast container
+│   │   ├── +layout.ts              # Root load: auth guard → redirect to /login if no token
+│   │   │
+│   │   ├── +page.svelte            # / → redirect to /files
+│   │   │
+│   │   ├── login/
+│   │   │   └── +page.svelte        # Login form (decorative Tanabata images)
+│   │   │
+│   │   ├── files/
+│   │   │   ├── +page.svelte        # File grid: filter bar, sort, multi-select, upload
+│   │   │   ├── +page.ts            # Load: initial file list (cursor page)
+│   │   │   ├── [id]/
+│   │   │   │   ├── +page.svelte    # File view: preview, metadata, tags, ACL
+│   │   │   │   └── +page.ts        # Load: file detail + tags
+│   │   │   └── trash/
+│   │   │       ├── +page.svelte    # Trash: restore / permanent delete
+│   │   │       └── +page.ts
+│   │   │
+│   │   ├── tags/
+│   │   │   ├── +page.svelte        # Tag list: search, sort, multi-select
+│   │   │   ├── +page.ts
+│   │   │   ├── new/
+│   │   │   │   └── +page.svelte    # Create tag form
+│   │   │   └── [id]/
+│   │   │       ├── +page.svelte    # Tag detail: edit, category, rules, parent tags
+│   │   │       └── +page.ts
+│   │   │
+│   │   ├── categories/
+│   │   │   ├── +page.svelte        # Category list
+│   │   │   ├── +page.ts
+│   │   │   ├── new/
+│   │   │   │   └── +page.svelte
+│   │   │   └── [id]/
+│   │   │       ├── +page.svelte    # Category detail: edit, view tags
+│   │   │       └── +page.ts
+│   │   │
+│   │   ├── pools/
+│   │   │   ├── +page.svelte        # Pool list
+│   │   │   ├── +page.ts
+│   │   │   ├── new/
+│   │   │   │   └── +page.svelte
+│   │   │   └── [id]/
+│   │   │       ├── +page.svelte    # Pool detail: files (reorderable), filter, edit
+│   │   │       └── +page.ts
+│   │   │
+│   │   ├── settings/
+│   │   │   ├── +page.svelte        # Profile: name, password, active sessions
+│   │   │   └── +page.ts
+│   │   │
+│   │   └── admin/
+│   │       ├── +layout.svelte      # Admin layout: restrict to is_admin
+│   │       ├── users/
+│   │       │   ├── +page.svelte    # User management list
+│   │       │   ├── +page.ts
+│   │       │   └── [id]/
+│   │       │       ├── +page.svelte # User detail: role, block/unblock
+│   │       │       └── +page.ts
+│   │       └── audit/
+│   │           ├── +page.svelte    # Audit log with filters
+│   │           └── +page.ts
+│   │
+│   └── service-worker.ts          # PWA: offline cache for pinned files, app shell caching
+│
+└── static/
+    ├── favicon.png
+    ├── favicon.ico
+    ├── manifest.webmanifest        # PWA manifest (name, icons, theme_color)
+    ├── images/
+    │   ├── tanabata-left.png       # Login page decorations (from current design)
+    │   ├── tanabata-right.png
+    │   └── icons/                  # PWA icons (192×192, 512×512, etc.)
+    └── fonts/
+        └── Epilogue-VariableFont_wght.ttf
+```
+
+## Key Architecture Decisions
+
+### CSS Hybrid: Tailwind + Custom Properties
+
+Theme colors defined as CSS custom properties in `app.css`:
+
+```css
+@tailwind base;
+@tailwind components;
+@tailwind utilities;
+
+:root {
+  --color-bg-primary: #312F45;
+  --color-bg-secondary: #181721;
+  --color-bg-elevated: #111118;
+  --color-accent: #9592B5;
+  --color-accent-hover: #7D7AA4;
+  --color-text-primary: #f0f0f0;
+  --color-text-muted: #9999AD;
+  --color-danger: #DB6060;
+  --color-info: #4DC7ED;
+  --color-warning: #F5E872;
+  --color-tag-default: #444455;
+}
+
+:root[data-theme="light"] {
+  --color-bg-primary: #f5f5f5;
+  --color-bg-secondary: #ffffff;
+  /* ... */
+}
+```
+
+Tailwind references them in `tailwind.config.ts`:
+
+```ts
+export default {
+  theme: {
+    extend: {
+      colors: {
+        bg: {
+          primary: 'var(--color-bg-primary)',
+          secondary: 'var(--color-bg-secondary)',
+          elevated: 'var(--color-bg-elevated)',
+        },
+        accent: {
+          DEFAULT: 'var(--color-accent)',
+          hover: 'var(--color-accent-hover)',
+        },
+        // ...
+      },
+      fontFamily: {
+        sans: ['Epilogue', 'sans-serif'],
+      },
+    },
+  },
+  darkMode: 'class', // controlled via data-theme attribute
+};
+```
+
+Usage in components: `<div class="bg-bg-primary text-text-primary rounded-xl p-4">`.
+Complex cases use scoped `<style>` inside `.svelte` files.
+
+### API Client Pattern
+
+`client.ts` — thin wrapper around fetch:
+
+```ts
+// $lib/api/client.ts
+import { authStore } from '$lib/stores/auth';
+
+const BASE = '/api/v1';
+
+async function request<T>(path: string, init?: RequestInit): Promise<T> {
+  const token = get(authStore).accessToken;
+  const res = await fetch(BASE + path, {
+    ...init,
+    headers: {
+      'Content-Type': 'application/json',
+      ...(token && { Authorization: `Bearer ${token}` }),
+      ...init?.headers,
+    },
+  });
+  if (res.status === 401) {
+    // attempt refresh, retry once
+  }
+  if (!res.ok) {
+    const err = await res.json();
+    throw new ApiError(res.status, err.code, err.message, err.details);
+  }
+  if (res.status === 204) return undefined as T;
+  return res.json();
+}
+
+export const api = {
+  get: <T>(path: string) => request<T>(path),
+  post: <T>(path: string, body?: unknown) =>
+    request<T>(path, { method: 'POST', body: JSON.stringify(body) }),
+  patch: <T>(path: string, body?: unknown) =>
+    request<T>(path, { method: 'PATCH', body: JSON.stringify(body) }),
+  put: <T>(path: string, body?: unknown) =>
+    request<T>(path, { method: 'PUT', body: JSON.stringify(body) }),
+  delete: <T>(path: string) => request<T>(path, { method: 'DELETE' }),
+  upload: <T>(path: string, formData: FormData) =>
+    request<T>(path, { method: 'POST', body: formData, headers: {} }),
+};
+```
+
+Domain-specific modules use it:
+
+```ts
+// $lib/api/files.ts
+import { api } from './client';
+import type { File, FileCursorPage } from './types';
+
+export function listFiles(params: Record<string, string>) {
+  const qs = new URLSearchParams(params).toString();
+  return api.get<FileCursorPage>(`/files?${qs}`);
+}
+
+export function uploadFile(formData: FormData) {
+  return api.upload<File>('/files', formData);
+}
+```
+
+### Type Generation
+
+Script in `package.json`:
+
+```json
+{
+  "scripts": {
+    "generate:types": "openapi-typescript ../openapi.yaml -o src/lib/api/schema.ts",
+    "dev": "npm run generate:types && vite dev",
+    "build": "npm run generate:types && vite build"
+  }
+}
+```
+
+Friendly aliases in `types.ts`:
+
+```ts
+import type { components } from './schema';
+
+export type File = components['schemas']['File'];
+export type Tag = components['schemas']['Tag'];
+export type Category = components['schemas']['Category'];
+export type Pool = components['schemas']['Pool'];
+export type FileCursorPage = components['schemas']['FileCursorPage'];
+export type TagOffsetPage = components['schemas']['TagOffsetPage'];
+export type Error = components['schemas']['Error'];
+// ...
+```
+
+### SPA Mode
+
+`svelte.config.js`:
+
+```js
+import adapter from '@sveltejs/adapter-static';
+
+export default {
+  kit: {
+    adapter: adapter({ fallback: 'index.html' }),
+    // SPA: all routes handled client-side
+  },
+};
+```
+
+The Go backend serves `index.html` for all non-API routes (SPA fallback).
+In development, Vite dev server proxies `/api` to the Go backend.
+
+### PWA
+
+`service-worker.ts` handles:
+- App shell caching (HTML, CSS, JS, fonts)
+- User-pinned file caching (explicit, via UI button)
+- Cache versioning and cleanup on update
+- Reset function (clear all caches except pinned files)

docs/GO_PROJECT_STRUCTURE.md

@@ -0,0 +1,320 @@
+# Tanabata File Manager — Go Project Structure
+
+## Stack
+
+- **Router**: Gin
+- **Database**: pgx v5 (pgxpool)
+- **Migrations**: goose v3 + go:embed (auto-migrate on startup)
+- **Auth**: JWT (golang-jwt/jwt/v5)
+- **Config**: environment variables via .env (joho/godotenv)
+- **Logging**: slog (stdlib, Go 1.21+)
+- **Validation**: go-playground/validator/v10
+- **EXIF**: rwcarlsen/goexif or dsoprea/go-exif
+- **Image processing**: disintegration/imaging (thumbnails, previews)
+- **Architecture**: Clean Architecture (domain → service → repository/handler)
+
+## Monorepo Layout
+
+```
+tanabata/
+├── backend/                            ← Go project
+├── frontend/                           ← SvelteKit project
+├── openapi.yaml                        ← Shared API contract
+├── docker-compose.yml
+├── Dockerfile
+├── .env.example
+└── README.md
+```
+
+## Backend Directory Layout
+
+```
+backend/
+├── cmd/
+│   └── server/
+│       └── main.go                     # Entrypoint: config → DB → migrate → wire → run
+│
+├── internal/
+│   │
+│   ├── domain/                         # Pure business entities & value objects
+│   │   ├── file.go                     # File, FileFilter, FilePage
+│   │   ├── tag.go                      # Tag, TagRule
+│   │   ├── category.go                 # Category
+│   │   ├── pool.go                     # Pool, PoolFile
+│   │   ├── user.go                     # User, Session
+│   │   ├── acl.go                      # Permission, ObjectType
+│   │   ├── audit.go                    # AuditEntry, ActionType
+│   │   └── errors.go                   # Domain error types (ErrNotFound, ErrForbidden, etc.)
+│   │
+│   ├── port/                           # Interfaces (ports) — contracts between layers
+│   │   ├── repository.go              # FileRepo, TagRepo, CategoryRepo, PoolRepo,
+│   │   │                               # UserRepo, SessionRepo, ACLRepo, AuditRepo,
+│   │   │                               # MimeRepo, TagRuleRepo
+│   │   └── storage.go                 # FileStorage interface (disk operations)
+│   │
+│   ├── service/                        # Business logic (use cases)
+│   │   ├── file_service.go             # Upload, update, delete, trash/restore, replace,
+│   │   │                               # import, filter/list, duplicate detection
+│   │   ├── tag_service.go              # CRUD + auto-tag application logic
+│   │   ├── category_service.go         # CRUD (thin, delegates to repo + ACL + audit)
+│   │   ├── pool_service.go             # CRUD + file ordering, add/remove files
+│   │   ├── auth_service.go             # Login, logout, JWT issue/refresh, session management
+│   │   ├── acl_service.go              # Permission checks, grant/revoke
+│   │   ├── audit_service.go            # Log actions, query audit log
+│   │   └── user_service.go             # Profile update, admin CRUD, block/unblock
+│   │
+│   ├── handler/                        # HTTP layer (Gin handlers)
+│   │   ├── router.go                   # Route registration, middleware wiring
+│   │   ├── middleware.go               # Auth middleware (JWT extraction → context)
+│   │   ├── request.go                  # Common request parsing helpers
+│   │   ├── response.go                 # Error/success response builders
+│   │   ├── file_handler.go             # /files endpoints
+│   │   ├── tag_handler.go              # /tags endpoints
+│   │   ├── category_handler.go         # /categories endpoints
+│   │   ├── pool_handler.go             # /pools endpoints
+│   │   ├── auth_handler.go             # /auth endpoints
+│   │   ├── acl_handler.go              # /acl endpoints
+│   │   ├── user_handler.go             # /users endpoints
+│   │   └── audit_handler.go            # /audit endpoints
+│   │
+│   ├── db/                             # Database adapters
+│   │   ├── db.go                       # Common helpers: pagination, repo factory, transactor base
+│   │   └── postgres/                   # PostgreSQL implementation
+│   │       ├── postgres.go             # pgxpool init, tx-from-context helpers
+│   │       ├── file_repo.go            # FileRepo implementation
+│   │       ├── tag_repo.go             # TagRepo + TagRuleRepo implementation
+│   │       ├── category_repo.go        # CategoryRepo implementation
+│   │       ├── pool_repo.go            # PoolRepo implementation
+│   │       ├── user_repo.go            # UserRepo implementation
+│   │       ├── session_repo.go         # SessionRepo implementation
+│   │       ├── acl_repo.go             # ACLRepo implementation
+│   │       ├── audit_repo.go           # AuditRepo implementation
+│   │       ├── mime_repo.go            # MimeRepo implementation
+│   │       └── filter_parser.go        # DSL → SQL WHERE clause builder
+│   │
+│   ├── storage/                        # File storage adapter
+│   │   └── disk.go                     # FileStorage implementation (read/write/delete on disk)
+│   │
+│   └── config/                         # Configuration
+│       └── config.go                   # Struct + loader from env vars
+│
+├── migrations/                         # SQL migration files (goose format)
+│   ├── 001_init_schemas.sql
+│   ├── 002_core_tables.sql
+│   ├── 003_data_tables.sql
+│   ├── 004_acl_tables.sql
+│   ├── 005_activity_tables.sql
+│   ├── 006_indexes.sql
+│   └── 007_seed_data.sql
+│
+├── go.mod
+└── go.sum
+```
+
+## Layer Dependency Rules
+
+```
+handler  →  service  →  port (interfaces)  ←  db/postgres / storage
+                ↓
+              domain (entities, value objects, errors)
+```
+
+- **domain/**: zero imports from other internal packages. Only stdlib.
+- **port/**: imports only domain/. Defines interfaces.
+- **service/**: imports domain/ and port/. Never imports db/ or handler/.
+- **handler/**: imports domain/ and service/. Never imports db/.
+- **db/postgres/**: imports domain/, port/, and db/ (common helpers). Implements port interfaces.
+- **db/**: imports domain/ and port/. Shared utilities for all DB adapters.
+- **storage/**: imports domain/ and port/. Implements FileStorage.
+
+No layer may import a layer above it. No circular dependencies.
+
+## Key Design Decisions
+
+### Dependency Injection (Wiring)
+
+Manual wiring in `cmd/server/main.go`. No DI frameworks.
+
+```go
+// Pseudocode
+pool := postgres.NewPool(cfg.DatabaseURL)
+goose.Up(pool, migrations)
+
+// Repos (all from internal/db/postgres/)
+fileRepo   := postgres.NewFileRepo(pool)
+tagRepo    := postgres.NewTagRepo(pool)
+// ...
+
+// Storage
+diskStore  := storage.NewDiskStorage(cfg.FilesPath)
+
+// Services
+aclSvc     := service.NewACLService(aclRepo, objectTypeRepo)
+auditSvc   := service.NewAuditService(auditRepo, actionTypeRepo)
+fileSvc    := service.NewFileService(fileRepo, mimeRepo, tagRepo, diskStore, aclSvc, auditSvc)
+tagSvc     := service.NewTagService(tagRepo, tagRuleRepo, aclSvc, auditSvc)
+// ...
+
+// Handlers
+fileHandler := handler.NewFileHandler(fileSvc, tagSvc)
+// ...
+
+router := handler.NewRouter(cfg, fileHandler, tagHandler, ...)
+router.Run(cfg.ListenAddr)
+```
+
+### Context Propagation
+
+Every service method receives `context.Context` as the first argument.
+The handler extracts user info from JWT (via middleware) and puts it
+into context. Services read the current user from context for ACL checks
+and audit logging.
+
+```go
+// middleware.go
+func (m *AuthMiddleware) Handle(c *gin.Context) {
+    claims := parseJWT(c.GetHeader("Authorization"))
+    ctx := domain.WithUser(c.Request.Context(), claims.UserID, claims.IsAdmin)
+    c.Request = c.Request.WithContext(ctx)
+    c.Next()
+}
+
+// domain/context.go
+type ctxKey int
+const userKey ctxKey = iota
+func WithUser(ctx context.Context, userID int16, isAdmin bool) context.Context { ... }
+func UserFromContext(ctx context.Context) (userID int16, isAdmin bool) { ... }
+```
+
+### Transaction Management
+
+Repository interfaces include a `Transactor`:
+
+```go
+// port/repository.go
+type Transactor interface {
+    WithTx(ctx context.Context, fn func(ctx context.Context) error) error
+}
+```
+
+The postgres implementation wraps `pgxpool.Pool.BeginTx`. Inside `fn`,
+all repo calls use the transaction from context. This allows services
+to compose multiple repo calls in a single transaction:
+
+```go
+// service/file_service.go
+func (s *FileService) Upload(ctx context.Context, input UploadInput) (*domain.File, error) {
+    return s.tx.WithTx(ctx, func(ctx context.Context) error {
+        file, err := s.fileRepo.Create(ctx, ...)  // uses tx
+        if err != nil { return err }
+        for _, tagID := range input.TagIDs {
+            s.tagRepo.AddFileTag(ctx, file.ID, tagID)  // same tx
+        }
+        s.auditRepo.Log(ctx, ...)  // same tx
+        return nil
+    })
+}
+```
+
+### ACL Check Pattern
+
+ACL logic is centralized in `ACLService`. Other services call it before
+any data mutation or retrieval:
+
+```go
+// service/acl_service.go
+func (s *ACLService) CanView(ctx context.Context, objectType string, objectID uuid.UUID) error {
+    userID, isAdmin := domain.UserFromContext(ctx)
+    if isAdmin { return nil }
+    // Check is_public on the object
+    // If not public, check creator_id == userID
+    // If not creator, check acl.permissions
+    // Return domain.ErrForbidden if none match
+}
+```
+
+### Error Mapping
+
+Domain errors → HTTP status codes (handled in handler/response.go):
+
+| Domain Error          | HTTP Status | Error Code        |
+|-----------------------|-------------|-------------------|
+| ErrNotFound           | 404         | not_found         |
+| ErrForbidden          | 403         | forbidden         |
+| ErrUnauthorized       | 401         | unauthorized      |
+| ErrConflict           | 409         | conflict          |
+| ErrValidation         | 400         | validation_error  |
+| ErrUnsupportedMIME    | 415         | unsupported_mime  |
+| (unexpected)          | 500         | internal_error    |
+
+### Filter DSL
+
+The DSL parser lives in `db/postgres/filter_parser.go` because it produces
+SQL WHERE clauses — it is a PostgreSQL-specific adapter concern.
+The service layer passes the raw DSL string to the repository; the
+repository parses it and builds the query.
+
+For a different DBMS, a corresponding parser would live in
+`db/<dbms>/filter_parser.go`.
+
+The interface:
+```go
+// port/repository.go
+type FileRepo interface {
+    List(ctx context.Context, params FileListParams) (*domain.FilePage, error)
+    // ...
+}
+
+// domain/file.go
+type FileListParams struct {
+    Filter    string    // raw DSL string
+    Sort      string
+    Order     string
+    Cursor    string
+    Anchor    *uuid.UUID
+    Direction string    // "forward" or "backward"
+    Limit     int
+    Trash     bool
+    Search    string
+}
+```
+
+### JWT Structure
+
+```go
+type Claims struct {
+    jwt.RegisteredClaims
+    UserID   int16 `json:"uid"`
+    IsAdmin  bool  `json:"adm"`
+    SessionID int  `json:"sid"`
+}
+```
+
+Access token: short-lived (15 min). Refresh token: long-lived (30 days),
+stored as hash in `activity.sessions.token_hash`.
+
+### Configuration (.env)
+
+```env
+# Server
+LISTEN_ADDR=:42776
+JWT_SECRET=<random-32-bytes>
+JWT_ACCESS_TTL=15m
+JWT_REFRESH_TTL=720h
+
+# Database
+DATABASE_URL=postgres://user:pass@host:5432/tanabata?sslmode=disable
+
+# Storage
+FILES_PATH=/data/files
+THUMBS_CACHE_PATH=/data/thumbs
+
+# Thumbnails
+THUMB_WIDTH=160
+THUMB_HEIGHT=160
+PREVIEW_WIDTH=1920
+PREVIEW_HEIGHT=1080
+
+# Import
+IMPORT_PATH=/data/import
+```

docs/reference/backend/cmd/main.go

@@ -0,0 +1,22 @@
+package main
+
+import (
+	"tanabata/internal/storage/postgres"
+)
+
+func main() {
+	postgres.InitDB("postgres://hiko:taikibansei@192.168.0.25/Tanabata_new?application_name=Tanabata%20testing")
+	// test_json := json.RawMessage([]byte("{\"valery\": \"ponosoff\"}"))
+	// data, statusCode, err := db.FileGetSlice(1, "", "+2", -2, 0)
+	// data, statusCode, err := db.FileGet(1, "0197d056-cfb0-76b5-97e0-bd588826393c")
+	// data, statusCode, err := db.FileAdd(1, "ABOBA.png", "image/png", time.Now(), "slkdfjsldkflsdkfj;sldkf", test_json)
+	// statusCode, err := db.FileUpdate(2, "0197d159-bf3a-7617-a3a8-a4a9fc39eca6", map[string]interface{}{
+	// 	"name": "ponos.png",
+	// })
+	// statusCode, err := db.FileDelete(1, "0197d155-848f-7221-ba4a-4660f257c7d5")
+	// v, e, err := postgres.FileGetAccess(1, "0197d15a-57f9-712c-991e-c512290e774f")
+	// fmt.Printf("V: %s, E: %s\n", v, e)
+	// fmt.Printf("Status: %d\n", statusCode)
+	// fmt.Printf("Error:  %s\n", err)
+	// fmt.Printf("%+v\n", data)
+}

docs/reference/backend/cmd/main.sync-conflict-20251008-195720-BYUI6ZC.go

@@ -0,0 +1,22 @@
+package main
+
+import (
+	"fmt"
+
+	"tanabata/db"
+)
+
+func main() {
+	db.InitDB("postgres://hiko:taikibansei@192.168.0.25/Tanabata_new?application_name=Tanabata%20testing")
+	// test_json := json.RawMessage([]byte("{\"valery\": \"ponosoff\"}"))
+	// data, statusCode, err := db.FileGetSlice(2, "", "+2", -2, 0)
+	// data, statusCode, err := db.FileGet(1, "0197d056-cfb0-76b5-97e0-bd588826393c")
+	// data, statusCode, err := db.FileAdd(1, "ABOBA.png", "image/png", time.Now(), "slkdfjsldkflsdkfj;sldkf", test_json)
+	// statusCode, err := db.FileUpdate(2, "0197d159-bf3a-7617-a3a8-a4a9fc39eca6", map[string]interface{}{
+	// 	"name": "ponos.png",
+	// })
+	statusCode, err := db.FileDelete(1, "0197d155-848f-7221-ba4a-4660f257c7d5")
+	fmt.Printf("Status: %d\n", statusCode)
+	fmt.Printf("Error:  %s\n", err)
+	// fmt.Printf("%+v\n", data)
+}

docs/reference/backend/db/db.go

@@ -0,0 +1,79 @@
+package db
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+var connPool *pgxpool.Pool
+
+func InitDB(connString string) error {
+	poolConfig, err := pgxpool.ParseConfig(connString)
+	if err != nil {
+		return fmt.Errorf("error while parsing connection string: %w", err)
+	}
+
+	poolConfig.MaxConns = 100
+	poolConfig.MinConns = 0
+	poolConfig.MaxConnLifetime = time.Hour
+	poolConfig.HealthCheckPeriod = 30 * time.Second
+
+	connPool, err = pgxpool.NewWithConfig(context.Background(), poolConfig)
+	if err != nil {
+		return fmt.Errorf("error while initializing DB connections pool: %w", err)
+	}
+	return nil
+}
+
+func transaction(handler func(context.Context, pgx.Tx) (statusCode int, err error)) (statusCode int, err error) {
+	ctx := context.Background()
+	tx, err := connPool.Begin(ctx)
+	if err != nil {
+		statusCode = http.StatusInternalServerError
+		return
+	}
+	statusCode, err = handler(ctx, tx)
+	if err != nil {
+		tx.Rollback(ctx)
+		return
+	}
+	err = tx.Commit(ctx)
+	if err != nil {
+		statusCode = http.StatusInternalServerError
+	}
+	return
+}
+
+// Handle database error
+func handleDBError(errIn error) (statusCode int, err error) {
+	if errIn == nil {
+		statusCode = http.StatusOK
+		return
+	}
+	if errors.Is(errIn, pgx.ErrNoRows) {
+		err = fmt.Errorf("not found")
+		statusCode = http.StatusNotFound
+		return
+	}
+	var pgErr *pgconn.PgError
+	if errors.As(errIn, &pgErr) {
+		switch pgErr.Code {
+		case "22P02", "22007": // Invalid data format
+			err = fmt.Errorf("%s", pgErr.Message)
+			statusCode = http.StatusBadRequest
+			return
+		case "23505": // Unique constraint violation
+			err = fmt.Errorf("already exists")
+			statusCode = http.StatusConflict
+			return
+		}
+	}
+	return http.StatusInternalServerError, errIn
+}

docs/reference/backend/db/utils.go

@@ -0,0 +1,53 @@
+package db
+
+import (
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+)
+
+// Convert "filter" URL param to SQL "WHERE" condition
+func filterToSQL(filter string) (sql string, statusCode int, err error) {
+	// filterTokens := strings.Split(string(filter), ";")
+	sql = "(true)"
+	return
+}
+
+// Convert "sort" URL param to SQL "ORDER BY"
+func sortToSQL(sort string) (sql string, statusCode int, err error) {
+	if sort == "" {
+		return
+	}
+	sortOptions := strings.Split(sort, ",")
+	sql = " ORDER BY "
+	for i, sortOption := range sortOptions {
+		sortOrder := sortOption[:1]
+		sortColumn := sortOption[1:]
+		// parse sorting order marker
+		switch sortOrder {
+		case "+":
+			sortOrder = "ASC"
+		case "-":
+			sortOrder = "DESC"
+		default:
+			err = fmt.Errorf("invalid sorting order mark: %q", sortOrder)
+			statusCode = http.StatusBadRequest
+			return
+		}
+		// validate sorting column
+		var n int
+		n, err = strconv.Atoi(sortColumn)
+		if err != nil || n < 0 {
+			err = fmt.Errorf("invalid sorting column: %q", sortColumn)
+			statusCode = http.StatusBadRequest
+			return
+		}
+		// add sorting option to query
+		if i > 0 {
+			sql += ","
+		}
+		sql += fmt.Sprintf("%s %s NULLS LAST", sortColumn, sortOrder)
+	}
+	return
+}

docs/reference/backend/go.mod

@@ -0,0 +1,19 @@
+module tanabata
+
+go 1.23.0
+
+toolchain go1.23.10
+
+require github.com/jackc/pgx/v5 v5.7.5
+
+require (
+	github.com/jackc/pgpassfile v1.0.0 // indirect
+	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
+	github.com/jackc/pgx v3.6.2+incompatible // indirect
+	github.com/jackc/puddle/v2 v2.2.2 // indirect
+	github.com/pkg/errors v0.9.1 // indirect
+	github.com/stretchr/testify v1.9.0 // indirect
+	golang.org/x/crypto v0.37.0 // indirect
+	golang.org/x/sync v0.13.0 // indirect
+	golang.org/x/text v0.24.0 // indirect
+)

docs/reference/backend/go.sum

@@ -0,0 +1,32 @@
+github.com/davecgh/go-spew v1.1.0/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/davecgh/go-spew v1.1.1 h1:vj9j/u1bqnvCEfJOwUhtlOARqs3+rkHYY13jYWTU97c=
+github.com/davecgh/go-spew v1.1.1/go.mod h1:J7Y8YcW2NihsgmVo/mv3lAwl/skON4iLHjSsI+c5H38=
+github.com/jackc/pgpassfile v1.0.0 h1:/6Hmqy13Ss2zCq62VdNG8tM1wchn8zjSGOBJ6icpsIM=
+github.com/jackc/pgpassfile v1.0.0/go.mod h1:CEx0iS5ambNFdcRtxPj5JhEz+xB6uRky5eyVu/W2HEg=
+github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 h1:iCEnooe7UlwOQYpKFhBabPMi4aNAfoODPEFNiAnClxo=
+github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761/go.mod h1:5TJZWKEWniPve33vlWYSoGYefn3gLQRzjfDlhSJ9ZKM=
+github.com/jackc/pgx v3.6.2+incompatible h1:2zP5OD7kiyR3xzRYMhOcXVvkDZsImVXfj+yIyTQf3/o=
+github.com/jackc/pgx v3.6.2+incompatible/go.mod h1:0ZGrqGqkRlliWnWB4zKnWtjbSWbGkVEFm4TeybAXq+I=
+github.com/jackc/pgx/v5 v5.7.5 h1:JHGfMnQY+IEtGM63d+NGMjoRpysB2JBwDr5fsngwmJs=
+github.com/jackc/pgx/v5 v5.7.5/go.mod h1:aruU7o91Tc2q2cFp5h4uP3f6ztExVpyVv88Xl/8Vl8M=
+github.com/jackc/puddle/v2 v2.2.2 h1:PR8nw+E/1w0GLuRFSmiioY6UooMp6KJv0/61nB7icHo=
+github.com/jackc/puddle/v2 v2.2.2/go.mod h1:vriiEXHvEE654aYKXXjOvZM39qJ0q+azkZFrfEOc3H4=
+github.com/pkg/errors v0.9.1 h1:FEBLx1zS214owpjy7qsBeixbURkuhQAwrK5UwLGTwt4=
+github.com/pkg/errors v0.9.1/go.mod h1:bwawxfHBFNV+L2hUp1rHADufV3IMtnDRdf1r5NINEl0=
+github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
+github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
+github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
+github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
+github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
+github.com/stretchr/testify v1.9.0 h1:HtqpIVDClZ4nwg75+f6Lvsy/wHu+3BoSGCbBAcpTsTg=
+github.com/stretchr/testify v1.9.0/go.mod h1:r2ic/lqez/lEtzL7wO/rwa5dbSLXVDPFyf8C91i36aY=
+golang.org/x/crypto v0.37.0 h1:kJNSjF/Xp7kU0iB2Z+9viTPMW4EqqsrywMXLJOOsXSE=
+golang.org/x/crypto v0.37.0/go.mod h1:vg+k43peMZ0pUMhYmVAWysMK35e6ioLh3wB8ZCAfbVc=
+golang.org/x/sync v0.13.0 h1:AauUjRAJ9OSnvULf/ARrrVywoJDy0YS2AwQ98I37610=
+golang.org/x/sync v0.13.0/go.mod h1:1dzgHSNfp02xaA81J2MS99Qcpr2w7fw1gpm99rleRqA=
+golang.org/x/text v0.24.0 h1:dd5Bzh4yt5KYA8f9CJHCP4FB4D51c2c6JvN37xJJkJ0=
+golang.org/x/text v0.24.0/go.mod h1:L8rBsPeo2pSS+xqN0d5u2ikmjtmoJbDBT1b7nHvFCdU=
+gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
+gopkg.in/yaml.v3 v3.0.0-20200313102051-9f266ea9e77c/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=
+gopkg.in/yaml.v3 v3.0.1 h1:fxVm/GzAzEWqLHuvctI91KS9hhNmmWOoWu0XTYJS7CA=
+gopkg.in/yaml.v3 v3.0.1/go.mod h1:K4uyk7z7BCEPqu6E+C64Yfv1cQ7kz7rIZviUmN+EgEM=

docs/reference/backend/internal/domain/domain.go

@@ -0,0 +1,122 @@
+package domain
+
+import (
+	"encoding/json"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgtype"
+)
+
+type User struct {
+	Name      string `json:"name"`
+	IsAdmin   bool   `json:"isAdmin"`
+	CanCreate bool   `json:"canCreate"`
+}
+
+type MIME struct {
+	Name      string `json:"name"`
+	Extension string `json:"extension"`
+}
+
+type (
+	CategoryCore struct {
+		ID    string      `json:"id"`
+		Name  string      `json:"name"`
+		Color pgtype.Text `json:"color"`
+	}
+	CategoryItem struct {
+		CategoryCore
+	}
+	CategoryFull struct {
+		CategoryCore
+		CreatedAt time.Time   `json:"createdAt"`
+		Creator   User        `json:"creator"`
+		Notes     pgtype.Text `json:"notes"`
+	}
+)
+
+type (
+	FileCore struct {
+		ID   string      `json:"id"`
+		Name pgtype.Text `json:"name"`
+		MIME MIME        `json:"mime"`
+	}
+	FileItem struct {
+		FileCore
+		CreatedAt time.Time `json:"createdAt"`
+		Creator   User      `json:"creator"`
+	}
+	FileFull struct {
+		FileCore
+		CreatedAt time.Time       `json:"createdAt"`
+		Creator   User            `json:"creator"`
+		Notes     pgtype.Text     `json:"notes"`
+		Metadata  json.RawMessage `json:"metadata"`
+		Tags      []TagCore       `json:"tags"`
+		Viewed    int             `json:"viewed"`
+	}
+)
+
+type (
+	TagCore struct {
+		ID    string      `json:"id"`
+		Name  string      `json:"name"`
+		Color pgtype.Text `json:"color"`
+	}
+	TagItem struct {
+		TagCore
+		Category CategoryCore `json:"category"`
+	}
+	TagFull struct {
+		TagCore
+		Category  CategoryCore `json:"category"`
+		CreatedAt time.Time    `json:"createdAt"`
+		Creator   User         `json:"creator"`
+		Notes     pgtype.Text  `json:"notes"`
+		UsedIncl  int          `json:"usedIncl"`
+		UsedExcl  int          `json:"usedExcl"`
+	}
+)
+
+type Autotag struct {
+	TriggerTag TagCore `json:"triggerTag"`
+	AddTag     TagCore `json:"addTag"`
+	IsActive   bool    `json:"isActive"`
+}
+
+type (
+	PoolCore struct {
+		ID   string `json:"id"`
+		Name string `json:"name"`
+	}
+	PoolItem struct {
+		PoolCore
+	}
+	PoolFull struct {
+		PoolCore
+		CreatedAt time.Time   `json:"createdAt"`
+		Creator   User        `json:"creator"`
+		Notes     pgtype.Text `json:"notes"`
+		Viewed    int         `json:"viewed"`
+	}
+)
+
+type Session struct {
+	ID           int       `json:"id"`
+	UserAgent    string    `json:"userAgent"`
+	StartedAt    time.Time `json:"startedAt"`
+	ExpiresAt    time.Time `json:"expiresAt"`
+	LastActivity time.Time `json:"lastActivity"`
+}
+
+type Pagination struct {
+	Total  int `json:"total"`
+	Offset int `json:"offset"`
+	Limit  int `json:"limit"`
+	Count  int `json:"count"`
+}
+
+type Slice[T any] struct {
+	Pagination Pagination `json:"pagination"`
+	Data       []T        `json:"data"`
+}

docs/reference/backend/internal/storage/postgres/auth.go

@@ -0,0 +1,16 @@
+package postgres
+
+import "context"
+
+func UserLogin(ctx context.Context, name, password string) (user_id int, err error) {
+	row := connPool.QueryRow(ctx, "SELECT id FROM users WHERE name=$1 AND password=crypt($2, password)", name, password)
+	err = row.Scan(&user_id)
+	return
+}
+
+func UserAuth(ctx context.Context, user_id int) (ok, isAdmin bool) {
+	row := connPool.QueryRow(ctx, "SELECT is_admin FROM users WHERE id=$1", user_id)
+	err := row.Scan(&isAdmin)
+	ok = (err == nil)
+	return
+}

docs/reference/backend/internal/storage/postgres/file.go

@@ -0,0 +1,268 @@
+package postgres
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"tanabata/internal/domain"
+)
+
+type FileStore struct {
+	db *pgxpool.Pool
+}
+
+func NewFileStore(db *pgxpool.Pool) *FileStore {
+	return &FileStore{db: db}
+}
+
+// Get user's access rights to file
+func (s *FileStore) getAccess(user_id int, file_id string) (canView, canEdit bool, err error) {
+	ctx := context.Background()
+	row := connPool.QueryRow(ctx, `
+		SELECT 
+			COALESCE(a.view, FALSE) OR f.creator_id=$1 OR COALESCE(u.is_admin, FALSE),
+			COALESCE(a.edit, FALSE) OR f.creator_id=$1 OR COALESCE(u.is_admin, FALSE)
+		FROM data.files f
+		LEFT JOIN acl.files a ON a.file_id=f.id AND a.user_id=$1
+		LEFT JOIN system.users u ON u.id=$1
+		WHERE f.id=$2
+		`, user_id, file_id)
+	err = row.Scan(&canView, &canEdit)
+	return
+}
+
+// Get a set of files
+func (s *FileStore) GetSlice(user_id int, filter, sort string, limit, offset int) (files domain.Slice[domain.FileItem], statusCode int, err error) {
+	filterCond, statusCode, err := filterToSQL(filter)
+	if err != nil {
+		return
+	}
+	sortExpr, statusCode, err := sortToSQL(sort)
+	if err != nil {
+		return
+	}
+	// prepare query
+	query := `
+	SELECT
+		f.id,
+		f.name,
+		m.name,
+		m.extension,
+		uuid_extract_timestamp(f.id),
+		u.name,
+		u.is_admin
+	FROM data.files f
+	JOIN system.mime m ON m.id=f.mime_id
+	JOIN system.users u ON u.id=f.creator_id
+	WHERE NOT f.is_deleted AND (f.creator_id=$1 OR (SELECT view FROM acl.files WHERE file_id=f.id AND user_id=$1) OR (SELECT is_admin FROM system.users WHERE id=$1)) AND
+	`
+	query += filterCond
+	queryCount := query
+	query += sortExpr
+	if limit >= 0 {
+		query += fmt.Sprintf(" LIMIT %d", limit)
+	}
+	if offset > 0 {
+		query += fmt.Sprintf(" OFFSET %d", offset)
+	}
+	// execute query
+	statusCode, err = transaction(func(ctx context.Context, tx pgx.Tx) (statusCode int, err error) {
+		rows, err := tx.Query(ctx, query, user_id)
+		if err != nil {
+			statusCode, err = handleDBError(err)
+			return
+		}
+		defer rows.Close()
+		count := 0
+		for rows.Next() {
+			var file domain.FileItem
+			err = rows.Scan(&file.ID, &file.Name, &file.MIME.Name, &file.MIME.Extension, &file.CreatedAt, &file.Creator.Name, &file.Creator.IsAdmin)
+			if err != nil {
+				statusCode = http.StatusInternalServerError
+				return
+			}
+			files.Data = append(files.Data, file)
+			count++
+		}
+		err = rows.Err()
+		if err != nil {
+			statusCode = http.StatusInternalServerError
+			return
+		}
+		files.Pagination.Limit = limit
+		files.Pagination.Offset = offset
+		files.Pagination.Count = count
+		row := tx.QueryRow(ctx, fmt.Sprintf("SELECT COUNT(*) FROM (%s) tmp", queryCount), user_id)
+		err = row.Scan(&files.Pagination.Total)
+		if err != nil {
+			statusCode = http.StatusInternalServerError
+		}
+		return
+	})
+	if err == nil {
+		statusCode = http.StatusOK
+	}
+	return
+}
+
+// Get file
+func (s *FileStore) Get(user_id int, file_id string) (file domain.FileFull, statusCode int, err error) {
+	ctx := context.Background()
+	row := connPool.QueryRow(ctx, `
+		SELECT
+			f.id,
+			f.name,
+			m.name,
+			m.extension,
+			uuid_extract_timestamp(f.id),
+			u.name,
+			u.is_admin,
+			f.notes,
+			f.metadata,
+			(SELECT COUNT(*) FROM activity.file_views fv WHERE fv.file_id=$2 AND fv.user_id=$1)
+		FROM data.files f
+		JOIN system.mime m ON m.id=f.mime_id
+		JOIN system.users u ON u.id=f.creator_id
+		WHERE NOT f.is_deleted AND f.id=$2 AND (f.creator_id=$1 OR (SELECT view FROM acl.files WHERE file_id=$2 AND user_id=$1) OR (SELECT is_admin FROM system.users WHERE id=$1))
+		`, user_id, file_id)
+	err = row.Scan(&file.ID, &file.Name, &file.MIME.Name, &file.MIME.Extension, &file.CreatedAt, &file.Creator.Name, &file.Creator.IsAdmin, &file.Notes, &file.Metadata, &file.Viewed)
+	if err != nil {
+		statusCode, err = handleDBError(err)
+		return
+	}
+	rows, err := connPool.Query(ctx, `
+		SELECT
+			t.id,
+			t.name,
+			COALESCE(t.color, c.color)
+		FROM data.tags t
+		LEFT JOIN data.categories c ON c.id=t.category_id
+		JOIN data.file_tag ft ON ft.tag_id=t.id
+		WHERE ft.file_id=$1
+		`, file_id)
+	if err != nil {
+		statusCode, err = handleDBError(err)
+		return
+	}
+	defer rows.Close()
+	for rows.Next() {
+		var tag domain.TagCore
+		err = rows.Scan(&tag.ID, &tag.Name, &tag.Color)
+		if err != nil {
+			statusCode = http.StatusInternalServerError
+			return
+		}
+		file.Tags = append(file.Tags, tag)
+	}
+	err = rows.Err()
+	if err != nil {
+		statusCode = http.StatusInternalServerError
+		return
+	}
+	statusCode = http.StatusOK
+	return
+}
+
+// Add file
+func (s *FileStore) Add(user_id int, name, mime string, datetime time.Time, notes string, metadata json.RawMessage) (file domain.FileCore, statusCode int, err error) {
+	ctx := context.Background()
+	var mime_id int
+	var extension string
+	row := connPool.QueryRow(ctx, "SELECT id, extension FROM system.mime WHERE name=$1", mime)
+	err = row.Scan(&mime_id, &extension)
+	if err != nil {
+		if err == pgx.ErrNoRows {
+			err = fmt.Errorf("unsupported file type: %q", mime)
+			statusCode = http.StatusBadRequest
+		} else {
+			statusCode, err = handleDBError(err)
+		}
+		return
+	}
+	row = connPool.QueryRow(ctx, `
+	INSERT INTO data.files (name, mime_id, datetime, creator_id, notes, metadata)
+	VALUES (NULLIF($1, ''), $2, $3, $4, NULLIF($5 ,''), $6)
+	RETURNING id
+	`, name, mime_id, datetime, user_id, notes, metadata)
+	err = row.Scan(&file.ID)
+	if err != nil {
+		statusCode, err = handleDBError(err)
+		return
+	}
+	file.Name.String = name
+	file.Name.Valid = (name != "")
+	file.MIME.Name = mime
+	file.MIME.Extension = extension
+	statusCode = http.StatusOK
+	return
+}
+
+// Update file
+func (s *FileStore) Update(user_id int, file_id string, updates map[string]interface{}) (statusCode int, err error) {
+	if len(updates) == 0 {
+		err = fmt.Errorf("no fields provided for update")
+		statusCode = http.StatusBadRequest
+		return
+	}
+	writableFields := map[string]bool{
+		"name":     true,
+		"datetime": true,
+		"notes":    true,
+		"metadata": true,
+	}
+	query := "UPDATE data.files SET"
+	newValues := []interface{}{user_id}
+	count := 2
+	for field, value := range updates {
+		if !writableFields[field] {
+			err = fmt.Errorf("invalid field: %q", field)
+			statusCode = http.StatusBadRequest
+			return
+		}
+		query += fmt.Sprintf(" %s=NULLIF($%d, '')", field, count)
+		newValues = append(newValues, value)
+		count++
+	}
+	query += fmt.Sprintf(
+		" WHERE id=$%d AND (creator_id=$1 OR (SELECT edit FROM acl.files WHERE file_id=$%d AND user_id=$1) OR (SELECT is_admin FROM system.users WHERE id=$1))",
+		count, count)
+	newValues = append(newValues, file_id)
+	ctx := context.Background()
+	commandTag, err := connPool.Exec(ctx, query, newValues...)
+	if err != nil {
+		statusCode, err = handleDBError(err)
+		return
+	}
+	if commandTag.RowsAffected() == 0 {
+		err = fmt.Errorf("not found")
+		statusCode = http.StatusNotFound
+		return
+	}
+	statusCode = http.StatusNoContent
+	return
+}
+
+// Delete file
+func (s *FileStore) Delete(user_id int, file_id string) (statusCode int, err error) {
+	ctx := context.Background()
+	commandTag, err := connPool.Exec(ctx,
+		"DELETE FROM data.files WHERE id=$2 AND (creator_id=$1 OR (SELECT edit FROM acl.files WHERE file_id=$2 AND user_id=$1) OR (SELECT is_admin FROM system.users WHERE id=$1))",
+		user_id, file_id)
+	if err != nil {
+		statusCode, err = handleDBError(err)
+		return
+	}
+	if commandTag.RowsAffected() == 0 {
+		err = fmt.Errorf("not found")
+		statusCode = http.StatusNotFound
+		return
+	}
+	statusCode = http.StatusNoContent
+	return
+}

docs/reference/backend/internal/storage/postgres/store.go

@@ -0,0 +1,92 @@
+package postgres
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"net/http"
+	"time"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgconn"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+type Storage struct {
+	db *pgxpool.Pool
+}
+
+var connPool *pgxpool.Pool
+
+// Initialize new database storage
+func New(dbURL string) (*Storage, error) {
+	ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+	defer cancel()
+	config, err := pgxpool.ParseConfig(dbURL)
+	if err != nil {
+		return nil, fmt.Errorf("failed to parse DB URL: %w", err)
+	}
+	config.MaxConns = 10
+	config.MinConns = 2
+	config.HealthCheckPeriod = time.Minute
+	db, err := pgxpool.NewWithConfig(ctx, config)
+	if err != nil {
+		return nil, fmt.Errorf("failed to connect to database: %w", err)
+	}
+	err = db.Ping(ctx)
+	if err != nil {
+		return nil, fmt.Errorf("database ping failed: %w", err)
+	}
+	return &Storage{db: db}, nil
+}
+
+// Close database storage
+func (s *Storage) Close() {
+	s.db.Close()
+}
+
+// Run handler inside transaction
+func (s *Storage) transaction(ctx context.Context, handler func(context.Context, pgx.Tx) (statusCode int, err error)) (statusCode int, err error) {
+	tx, err := connPool.Begin(ctx)
+	if err != nil {
+		statusCode = http.StatusInternalServerError
+		return
+	}
+	statusCode, err = handler(ctx, tx)
+	if err != nil {
+		tx.Rollback(ctx)
+		return
+	}
+	err = tx.Commit(ctx)
+	if err != nil {
+		statusCode = http.StatusInternalServerError
+	}
+	return
+}
+
+// Handle database error
+func (s *Storage) handleDBError(errIn error) (statusCode int, err error) {
+	if errIn == nil {
+		statusCode = http.StatusOK
+		return
+	}
+	if errors.Is(errIn, pgx.ErrNoRows) {
+		err = fmt.Errorf("not found")
+		statusCode = http.StatusNotFound
+		return
+	}
+	var pgErr *pgconn.PgError
+	if errors.As(errIn, &pgErr) {
+		switch pgErr.Code {
+		case "22P02", "22007": // Invalid data format
+			err = fmt.Errorf("%s", pgErr.Message)
+			statusCode = http.StatusBadRequest
+			return
+		case "23505": // Unique constraint violation
+			err = fmt.Errorf("already exists")
+			statusCode = http.StatusConflict
+			return
+		}
+	}
+	return http.StatusInternalServerError, errIn
+}

docs/reference/backend/internal/storage/postgres/utils.go

@@ -0,0 +1,53 @@
+package postgres
+
+import (
+	"fmt"
+	"net/http"
+	"strconv"
+	"strings"
+)
+
+// Convert "filter" URL param to SQL "WHERE" condition
+func filterToSQL(filter string) (sql string, statusCode int, err error) {
+	// filterTokens := strings.Split(string(filter), ";")
+	sql = "(true)"
+	return
+}
+
+// Convert "sort" URL param to SQL "ORDER BY"
+func sortToSQL(sort string) (sql string, statusCode int, err error) {
+	if sort == "" {
+		return
+	}
+	sortOptions := strings.Split(sort, ",")
+	sql = " ORDER BY "
+	for i, sortOption := range sortOptions {
+		sortOrder := sortOption[:1]
+		sortColumn := sortOption[1:]
+		// parse sorting order marker
+		switch sortOrder {
+		case "+":
+			sortOrder = "ASC"
+		case "-":
+			sortOrder = "DESC"
+		default:
+			err = fmt.Errorf("invalid sorting order mark: %q", sortOrder)
+			statusCode = http.StatusBadRequest
+			return
+		}
+		// validate sorting column
+		var n int
+		n, err = strconv.Atoi(sortColumn)
+		if err != nil || n < 0 {
+			err = fmt.Errorf("invalid sorting column: %q", sortColumn)
+			statusCode = http.StatusBadRequest
+			return
+		}
+		// add sorting option to query
+		if i > 0 {
+			sql += ","
+		}
+		sql += fmt.Sprintf("%s %s NULLS LAST", sortColumn, sortOrder)
+	}
+	return
+}

docs/reference/backend/internal/storage/storage.go

@@ -0,0 +1,21 @@
+package storage
+
+import (
+	"encoding/json"
+	"time"
+
+	"tanabata/internal/domain"
+)
+
+type Storage interface {
+	FileRepository
+	Close()
+}
+
+type FileRepository interface {
+	GetSlice(user_id int, filter, sort string, limit, offset int) (files domain.Slice[domain.FileItem], statusCode int, err error)
+	Get(user_id int, file_id string) (file domain.FileFull, statusCode int, err error)
+	Add(user_id int, name, mime string, datetime time.Time, notes string, metadata json.RawMessage) (file domain.FileCore, statusCode int, err error)
+	Update(user_id int, file_id string, updates map[string]interface{}) (statusCode int, err error)
+	Delete(user_id int, file_id string) (statusCode int, err error)
+}

docs/reference/backend/models/models.go

@@ -0,0 +1,120 @@
+package models
+
+import (
+	"encoding/json"
+	"time"
+
+	"github.com/jackc/pgx/v5/pgtype"
+)
+
+type User struct {
+	Name      string `json:"name"`
+	IsAdmin   bool   `json:"isAdmin"`
+	CanCreate bool   `json:"canCreate"`
+}
+
+type MIME struct {
+	Name      string `json:"name"`
+	Extension string `json:"extension"`
+}
+
+type (
+	CategoryCore struct {
+		ID    string      `json:"id"`
+		Name  string      `json:"name"`
+		Color pgtype.Text `json:"color"`
+	}
+	CategoryItem struct {
+		CategoryCore
+	}
+	CategoryFull struct {
+		CategoryCore
+		CreatedAt time.Time   `json:"createdAt"`
+		Creator   User        `json:"creator"`
+		Notes     pgtype.Text `json:"notes"`
+	}
+)
+
+type (
+	FileCore struct {
+		ID   string      `json:"id"`
+		Name pgtype.Text `json:"name"`
+		MIME MIME        `json:"mime"`
+	}
+	FileItem struct {
+		FileCore
+		CreatedAt time.Time `json:"createdAt"`
+		Creator   User      `json:"creator"`
+	}
+	FileFull struct {
+		FileCore
+		CreatedAt time.Time       `json:"createdAt"`
+		Creator   User            `json:"creator"`
+		Notes     pgtype.Text     `json:"notes"`
+		Metadata  json.RawMessage `json:"metadata"`
+		Tags      []TagCore       `json:"tags"`
+		Viewed    int             `json:"viewed"`
+	}
+)
+
+type (
+	TagCore struct {
+		ID    string      `json:"id"`
+		Name  string      `json:"name"`
+		Color pgtype.Text `json:"color"`
+	}
+	TagItem struct {
+		TagCore
+		Category CategoryCore `json:"category"`
+	}
+	TagFull struct {
+		TagCore
+		Category  CategoryCore `json:"category"`
+		CreatedAt time.Time    `json:"createdAt"`
+		Creator   User         `json:"creator"`
+		Notes     pgtype.Text  `json:"notes"`
+	}
+)
+
+type Autotag struct {
+	TriggerTag TagCore `json:"triggerTag"`
+	AddTag     TagCore `json:"addTag"`
+	IsActive   bool    `json:"isActive"`
+}
+
+type (
+	PoolCore struct {
+		ID   string `json:"id"`
+		Name string `json:"name"`
+	}
+	PoolItem struct {
+		PoolCore
+	}
+	PoolFull struct {
+		PoolCore
+		CreatedAt time.Time   `json:"createdAt"`
+		Creator   User        `json:"creator"`
+		Notes     pgtype.Text `json:"notes"`
+		Viewed    int         `json:"viewed"`
+	}
+)
+
+type Session struct {
+	ID           int       `json:"id"`
+	UserAgent    string    `json:"userAgent"`
+	StartedAt    time.Time `json:"startedAt"`
+	ExpiresAt    time.Time `json:"expiresAt"`
+	LastActivity time.Time `json:"lastActivity"`
+}
+
+type Pagination struct {
+	Total  int `json:"total"`
+	Offset int `json:"offset"`
+	Limit  int `json:"limit"`
+	Count  int `json:"count"`
+}
+
+type Slice[T any] struct {
+	Pagination Pagination `json:"pagination"`
+	Data       []T        `json:"data"`
+}