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  cache+server union via a request-id-tagged search-event, so superseded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/utils/podcastFilter.ts

@@ -0,0 +1,30 @@
+// HACK: hide "Podcasts" from the music library.
+//
+// The user stores podcasts inside the music library under a folder/album named
+// "Podcasts", so they leak into album/artist/track/playlist queries. Jellyfin's
+// item queries here don't give us a clean server-side exclusion for that folder,
+// so we filter client-side by name. This is intentionally a blunt instrument:
+// anything whose own name, album, or (album) artist is literally "Podcasts" is
+// dropped. If the folder is ever renamed, update PODCAST_FOLDER_NAME.
+import type { MediaItem } from "$lib/api/types";
+
+const PODCAST_FOLDER_NAME = "podcasts";
+
+function isPodcastName(value: string | null | undefined): boolean {
+  return value?.trim().toLowerCase() === PODCAST_FOLDER_NAME;
+}
+
+/** True when an item belongs to the "Podcasts" folder/album and should be hidden. */
+export function isPodcastItem(item: MediaItem): boolean {
+  return (
+    isPodcastName(item.name) ||
+    isPodcastName(item.albumName) ||
+    isPodcastName(item.albumArtist) ||
+    (item.artists?.some(isPodcastName) ?? false)
+  );
+}
+
+/** Remove "Podcasts" entries from a list of music items. */
+export function excludePodcasts(items: MediaItem[]): MediaItem[] {
+  return items.filter((item) => !isPodcastItem(item));
+}