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-tauri/src/lib.rs

@@ -522,6 +522,33 @@ async fn nd_delete_user(
     Ok(())
 }
 
+/// GET `/api/song?_sort=...&_order=...&_start=...&_end=...` — paginated song list.
+/// Available to any authenticated user (no admin required). Returns raw JSON array.
+#[tauri::command]
+async fn nd_list_songs(
+    server_url: String,
+    token: String,
+    sort: String,
+    order: String,
+    start: u32,
+    end: u32,
+) -> Result<serde_json::Value, String> {
+    let url = format!(
+        "{}/api/song?_sort={}&_order={}&_start={}&_end={}",
+        server_url, sort, order, start, end
+    );
+    let resp = nd_retry(|| {
+        nd_http_client()
+            .get(&url)
+            .header("X-ND-Authorization", format!("Bearer {}", token))
+            .send()
+    }).await?;
+    if !resp.status().is_success() {
+        return Err(format!("HTTP {}", resp.status()));
+    }
+    resp.json::<serde_json::Value>().await.map_err(nd_err)
+}
+
 /// GET `/api/library` — list all libraries (admin only). Returns the raw JSON array.
 #[tauri::command]
 async fn nd_list_libraries(
@@ -3838,6 +3865,7 @@ pub fn run() {
             nd_update_user,
             nd_delete_user,
             nd_list_libraries,
+            nd_list_songs,
             nd_set_user_libraries,
             nd_list_playlists,
             nd_create_playlist,