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  cache+server union via a request-id-tagged search-event, so superseded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-tauri/android/src/main/java/com/dtourolle/jellytau/player/JellyTauPlayer.kt

@@ -171,6 +171,12 @@ class JellyTauPlayer(private val appContext: Context) {
         // Create ExoPlayer with audio focus handling
         exoPlayer = ExoPlayer.Builder(appContext)
             .setAudioAttributes(audioAttributes, /* handleAudioFocus= */ true)
+            // Pause when the audio output is removed (wired headphones unplugged or
+            // Bluetooth device disconnected). ExoPlayer listens for the system
+            // ACTION_AUDIO_BECOMING_NOISY broadcast, which fires for both cases.
+            // The resulting pause flows through onIsPlayingChanged, keeping Rust and
+            // the lockscreen notification in sync automatically.
+            .setHandleAudioBecomingNoisy(true)
             .build()
 
         // Set up player listener