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/App.tsx

@@ -46,6 +46,7 @@ const LabelAlbums    = lazy(() => import('./pages/LabelAlbums'));
 const AdvancedSearch = lazy(() => import('./pages/AdvancedSearch'));
 const FolderBrowser  = lazy(() => import('./pages/FolderBrowser'));
 const InternetRadio  = lazy(() => import('./pages/InternetRadio'));
+const Tracks         = lazy(() => import('./pages/Tracks'));
 import MiniPlayer from './components/MiniPlayer';
 import { initMiniPlayerBridgeOnMain } from './utils/miniPlayerBridge';
 import FullscreenPlayer from './components/FullscreenPlayer';
@@ -445,6 +446,7 @@ function AppShell() {
               <Routes>
                 <Route path="/" element={<Home />} />
                 <Route path="/albums" element={<Albums />} />
+                <Route path="/tracks" element={<Tracks />} />
                 <Route path="/random" element={<RandomLanding />} />
                 <Route path="/random/albums" element={<RandomAlbums />} />
                 <Route path="/album/:id" element={<AlbumDetail />} />