feat(library): focused music/TV/movie landing screens + self-draining download queue

Library screens:
- Add dedicated music, TV, and movie landing pages (hero banner +
  horizontal carousels) backed by new music/tv/movies stores.
- Route tvshows libraries to /library/tv; surface rediscover ("haven't
  listened to in a while") albums via a new repository method across
  online/offline/hybrid repos plus the repository_get_rediscover_albums
  command.
- Add an A-Z jump bar for long alphabetically-sorted lists, with grid
  index anchors in LibraryGrid/LibraryListView/TrackList.
- Filter the "Podcasts" folder out of music library queries.

Downloads:
- Add a backend queue pump: enqueue_download / enqueue_video_downloads
  persist the resolved stream URL + target dir on each row (migration
  017), and the pump starts up to max_concurrent and drains the rest
  automatically as slots free, instead of the frontend silently dropping
  items past the concurrency limit. Album/series/season buttons now
  enqueue rather than calling start_download directly.

Other fixes:
- Hybrid search now returns instant cache results and pushes the merged
  cache+server union via a request-id-tagged search-event, so superseded
  queries can't clobber fresher results.
- URL-encode SearchTerm / genres / item types in online repo requests.
- Android: pause on audio-becoming-noisy (headphone/BT disconnect).

src/lib/api/repository-client.ts

@@ -109,12 +109,17 @@ export class RepositoryClient {
     return commands.repositoryGetResumeMovies(this.ensureHandle(), limit ?? null);
   }
 
+  /** Albums the user has played but not listened to recently ("rediscover"). */
+  async getRediscoverAlbums(parentId?: string, limit?: number): Promise<MediaItem[]> {
+    return commands.repositoryGetRediscoverAlbums(this.ensureHandle(), parentId ?? null, limit ?? null);
+  }
+
   async getGenres(parentId?: string): Promise<Genre[]> {
     return commands.repositoryGetGenres(this.ensureHandle(), parentId ?? null);
   }
 
-  async search(query: string, options?: SearchOptions): Promise<SearchResult> {
-    return commands.repositorySearch(this.ensureHandle(), query, options ?? null);
+  async search(query: string, options?: SearchOptions, requestId = 0): Promise<SearchResult> {
+    return commands.repositorySearch(this.ensureHandle(), query, options ?? null, requestId);
   }
 
   // ===== Playback Methods (all via Rust) =====