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/api/subsonic.ts

@@ -926,6 +926,23 @@ export async function search(query: string, options?: { albumCount?: number; art
   return { artists: r.artist ?? [], albums: r.album ?? [], songs: r.song ?? [] };
 }
 
+/**
+ * Song-only paginated search3. Tolerates empty query — Navidrome returns all songs
+ * ordered by title in that case; strict Subsonic implementations may return nothing.
+ * Caller handles empty results gracefully (Tracks page falls back to its random pool).
+ */
+export async function searchSongsPaged(query: string, songCount: number, songOffset: number): Promise<SubsonicSong[]> {
+  const data = await api<{ searchResult3: { song?: SubsonicSong[] } }>('search3.view', {
+    query,
+    artistCount: 0,
+    albumCount: 0,
+    songCount,
+    songOffset,
+    ...libraryFilterParams(),
+  });
+  return data.searchResult3?.song ?? [];
+}
+
 export async function setRating(id: string, rating: number): Promise<void> {
   await api('setRating.view', { id, rating });
 }