8afd3d9234
- Add published_snapshot (jsonb) and published_at (timestamp) columns
- New POST publish/{id} endpoint: stores snapshot JSON, locks editing
- New POST unpublish/{id} endpoint: clears published_at for editing
- Block update and sync_items when published_at is set
- Frontend detail page with conditional edit/publish/unpublish buttons
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>