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  cache+server union via a request-id-tagged search-event, so superseded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/components/library/SeasonDownloadButton.svelte

@@ -71,6 +71,13 @@
 
       // Pin the season item
       await downloads.pinItem(seasonId);
+
+      // Resolve each episode's transcode URL (server-side) and enqueue. The
+      // backend pump then starts up to max_concurrent and advances through the
+      // rest as slots free up.
+      const handle = auth.getRepository().getHandle();
+      await commands.enqueueVideoDownloads(handle, downloadIds, targetDir);
+      console.log("   Episodes enqueued; backend pump will start them");
     } catch (error) {
       console.error("Failed to start season download:", error);
     } finally {