feat(docs): version-bound release documentation served at /docs

Adds a docs pipeline so each release has a version-bound Markdown
document (docs/releases/vX.Y.Z.md) rendered publicly in the app:

- sync-release-docs.mjs copies docs/releases/*.md into the toolrate
  public dir and generates index.json before every dev/build
- /docs lists all releases; /docs/:version renders the sanitized
  Markdown (marked + DOMPurify, typography styles)
- template + workflow documented in docs/README.md
- current release (v0.6.0) documented as the first entry

pnpm-workspace.yaml

@@ -61,9 +61,11 @@ catalog:
   '@vitejs/plugin-react': 6.0.5
   class-variance-authority: 0.7.1
   clsx: 2.1.1
+  dompurify: 3.4.12
   drizzle-orm: 0.45.2
   framer-motion: 12.43.0
   lucide-react: 1.28.0
+  marked: 18.0.7
   react: 19.2.8
   react-dom: 19.2.8
   tailwind-merge: 3.6.0