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/navidromeBrowse.ts

@@ -0,0 +1,97 @@
+import { invoke } from '@tauri-apps/api/core';
+import { useAuthStore } from '../store/authStore';
+import { ndLogin } from './navidromeAdmin';
+import type { SubsonicSong } from './subsonic';
+
+/** Server-keyed Bearer token cache. Cheap to keep — Navidrome tokens are long-lived. */
+let cachedToken: { serverUrl: string; token: string } | null = null;
+
+async function getToken(force = false): Promise<string> {
+  const { getActiveServer, getBaseUrl } = useAuthStore.getState();
+  const server = getActiveServer();
+  const baseUrl = getBaseUrl();
+  if (!server || !baseUrl) throw new Error('No active server configured');
+  if (!force && cachedToken?.serverUrl === baseUrl) return cachedToken.token;
+  const result = await ndLogin(baseUrl, server.username, server.password);
+  cachedToken = { serverUrl: baseUrl, token: result.token };
+  return result.token;
+}
+
+function asString(v: unknown, fallback = ''): string {
+  return typeof v === 'string' ? v : (typeof v === 'number' ? String(v) : fallback);
+}
+
+function asNumber(v: unknown): number | undefined {
+  return typeof v === 'number' && isFinite(v) ? v : undefined;
+}
+
+function mapNdSong(o: Record<string, unknown>): SubsonicSong {
+  // Navidrome's REST shape differs from Subsonic — flatten into the SubsonicSong contract.
+  const id = asString(o.id ?? o.mediaFileId);
+  const albumId = asString(o.albumId);
+  return {
+    id,
+    title: asString(o.title),
+    artist: asString(o.artist),
+    album: asString(o.album),
+    albumId,
+    artistId: asString(o.artistId) || undefined,
+    duration: asNumber(o.duration) !== undefined ? Math.round(asNumber(o.duration)!) : 0,
+    track: asNumber(o.trackNumber),
+    discNumber: asNumber(o.discNumber),
+    // Navidrome usually exposes coverArtId; many builds also accept the song id directly.
+    coverArt: asString(o.coverArtId) || albumId || id || undefined,
+    year: asNumber(o.year),
+    userRating: asNumber(o.rating),
+    starred: o.starred ? asString(o.starredAt) || 'true' : undefined,
+    genre: typeof o.genre === 'string' ? o.genre : undefined,
+    bitRate: asNumber(o.bitRate),
+    suffix: typeof o.suffix === 'string' ? o.suffix : undefined,
+    contentType: typeof o.contentType === 'string' ? o.contentType : undefined,
+    size: asNumber(o.size),
+    samplingRate: asNumber(o.sampleRate),
+    bitDepth: asNumber(o.bitDepth),
+  };
+}
+
+export type NdSongSort = 'title' | 'artist' | 'album' | 'recently_added' | 'play_count';
+
+/**
+ * Fetch a sorted, paginated slice of all songs via Navidrome's native REST API.
+ * Returns mapped SubsonicSong objects. Throws on auth failure or non-Navidrome.
+ */
+export async function ndListSongs(
+  start: number,
+  end: number,
+  sort: NdSongSort = 'title',
+  order: 'ASC' | 'DESC' = 'ASC',
+): Promise<SubsonicSong[]> {
+  const baseUrl = useAuthStore.getState().getBaseUrl();
+  if (!baseUrl) throw new Error('No server configured');
+
+  const callOnce = async (token: string): Promise<unknown> =>
+    invoke<unknown>('nd_list_songs', { serverUrl: baseUrl, token, sort, order, start, end });
+
+  let token = await getToken();
+  let raw: unknown;
+  try {
+    raw = await callOnce(token);
+  } catch (err) {
+    const msg = String(err);
+    // Token rejected → re-auth once and retry
+    if (msg.includes('401') || msg.includes('403')) {
+      token = await getToken(true);
+      raw = await callOnce(token);
+    } else {
+      throw err;
+    }
+  }
+
+  if (!Array.isArray(raw)) return [];
+  return raw.map(s => mapNdSong(s as Record<string, unknown>));
+}
+
+/** Drop the cached token — call when the active server changes. */
+export function ndClearTokenCache(): void {
+  cachedToken = null;
+}