- Add /api/admin/thumbnail/[id] proxy endpoint for serving Immich thumbnails
- Show album cover thumbnails in AlbumCard components (subpages + standalone)
- Show actual image thumbnails in AlbumPicker modal instead of emoji placeholders
- Show small thumbnail previews for hero image entries
- Add corresponding CSS styles for all thumbnail elements
- Add /admin route with password-protected visual page builder
- Page Builder: manage hero images, standalone albums, subpages, and sections
- Album Picker: browse all shared Immich albums with search and filtering
- Settings Editor: theme, grid, footer, legal, SEO configuration
- YAML service with atomic writes and automatic backups (content/.backups/)
- HMAC-signed admin sessions (24h expiry, HttpOnly cookies)
- API endpoints: /api/admin/{auth,gallery,settings,albums,reload}
- Enable with ADMIN_PASSWORD env var; disabled by default
- invalidateConfigCache() export for hot-reload after saves
