refactor: split monolithic migration into 7 goose files

001_init_schemas  — extensions, schemas, uuid_v7 functions
002_core_tables   — core.users, mime_types, object_types
003_data_tables   — data.categories, tags, tag_rules, files, file_tag, pools, file_pool
004_acl_tables    — acl.permissions
005_activity_tables — activity.action_types, sessions, file_views, pool_views, tag_uses, audit_log
006_indexes       — all indexes across all schemas
007_seed_data     — object_types and action_types reference rows

Each file has -- +goose Up / Down annotations; downs drop in reverse
dependency order.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

backend/migrations/007_seed_data.sql

@@ -0,0 +1,32 @@
+-- +goose Up
+
+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');
+
+-- +goose Down
+
+DELETE FROM activity.action_types;
+DELETE FROM core.object_types;