Shot annotations: markdown comments, star rating, and persistent metadata

[hessius]

Closed by #262 — v2.2.0 released.

[hessius]

Implementation Status: ⚠️ Partial

PR #262 implements the core shot annotation system with markdown comments, but not star ratings.

Implemented:

• ✅ shot_annotations_service.py with JSON storage keyed by {date}/{filename}
• ✅ GET /api/shots/{date}/{filename}/annotation endpoint
• ✅ PATCH /api/shots/{date}/{filename}/annotation endpoint
• ✅ MarkdownEditor.tsx component with edit/preview toggle, character counter
• ✅ ShotAnnotation.tsx wrapper component
• ✅ Inline markdown comment editing in ShotHistoryView
• ✅ Auto-save on blur with toast feedback

Outstanding for full #179 completion:

• ❌ Star rating (1-5) UI and storage
• ❌ DELETE /api/shots/annotation/{shot_id} endpoint
• ❌ Annotated shots flagged in shot list (stars + comment icon)
• ❌ Retention policy (pinned shots exempt from cache rotation)

The MarkdownEditor component is fully built and reused in #225 (profile notes). Star rating can be added as an incremental enhancement.