* feat(admin): implement visual theme cards, album search, and system status diagnostics
* fix(admin): resolve type-checking build errors in SettingsEditor and status route
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Co-authored-by: ralksta <ralksta@users.noreply.github.com>
- Asset Picker: Visual browser for hero images with Favorites tab (shown first)
and All Photos tab. Includes infinite scroll and UUID fallback input for
assets not easily found in the grid.
- Drag & Drop: All lists (hero images, standalone albums, subpage albums,
subpage tiles) are now reorderable via drag handles using @dnd-kit.
- Preview Links: 'Preview Site' button in save bar, '↗ Site' in header, and
per-subpage preview links with URL slug preview shown inline.
- Keyboard Shortcuts: ⌘+S / Ctrl+S to save in both Pages and Settings tabs.
- Unsaved Changes Guard: beforeunload warning prevents accidental data loss.
- New API route /api/admin/assets for browsing Immich assets with pagination
and favorites filter via search/metadata endpoint.
- 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
