chore(project): drop the docs/reference Flask snapshot

The previous Python/Flask app under docs/reference/ was kept as a visual
design reference while bootstrapping the new frontend. That's well past
done, and 85 files of dead code just add noise to search and exploration.
Remove it (recoverable from history if needed) and update CLAUDE.md: keep
the design tokens, drop the now-dead pointer at the folder.

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

CLAUDE.md

@@ -21,8 +21,8 @@ Monorepo: `backend/` (Go) + `frontend/` (SvelteKit).
 
 ## Design reference
 
-The `docs/reference/` directory contains the previous Python/Flask version.
-Use its visual design as the basis for the new frontend:
+Visual design tokens for the frontend (carried over from the previous
+Python/Flask version):
 - Color palette: #312F45 (bg), #9592B5 (accent), #444455 (tag default), #111118 (elevated)
 - Font: Epilogue (variable weight)
 - Dark theme is primary
@@ -55,4 +55,4 @@ npm run generate:types       # regenerate API types from openapi.yaml
 - 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)
+  - `(project)` for root-level files (.gitignore, docs, structure)