feat(tracks): add Tracks library hub page (closes #299) (#300)

New /tracks route with three sections:

- Hero "Track of the moment" — random pick with play / enqueue / reroll
- Random Pick rail — 18 song cards, rerollable; hero song deduped
- Browse all tracks — virtualized list (@tanstack/react-virtual),
  paginated 50 at a time

Browse uses Navidrome's native /api/song?_sort=title&_order=ASC for
proper A-Z order (no Subsonic equivalent), with automatic fallback
to search3 on non-Navidrome servers. Search input drives search3
with 300ms debounce. Bearer token cached module-level, re-auth on 401.

Play button on rows + cards calls a new enqueueAndPlay() helper that
appends to the existing queue (skip if duplicate) and jumps to the
song — different from playSongNow which replaces the queue. Enqueue
button stays opaque (no hover-only).

i18n keys for sidebar.tracks + tracks.* namespace in all 8 locales.
New AudioLines sidebar icon. Sidebar entry inserted between
"All Albums" and "Build a Mix".

Performance: cover thumbnails dropped (uniform layout instead),
RAF-throttled scroll prefetch, hover transforms removed from cards
(WebKitGTK compositing-friendly).

Co-authored-by: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/main.tsx

@@ -7,6 +7,7 @@ import './i18n';
 import './styles/theme.css';
 import './styles/layout.css';
 import './styles/components.css';
+import './styles/tracks.css';
 
 // Expose the Tauri window label synchronously so App() can pick its root
 // component (main app vs mini player) on first render without flicker.