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  cache+server union via a request-id-tagged search-event, so superseded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

@@ -0,0 +1,161 @@
+// Movies library landing page data store.
+// Powers the focused movies landing: hero + horizontal sliders.
+// TRACES: UR-007, UR-023, UR-034 | DR-007, DR-038, DR-039
+import { writable, derived } from "svelte/store";
+import type { MediaItem } from "$lib/api/types";
+import { auth } from "./auth";
+
+/** A single "by genre" row: the genre name plus the movies in it. */
+export interface GenreRow {
+  id: string;
+  name: string;
+  items: MediaItem[];
+}
+
+interface MoviesState {
+  // Movies the user can resume (continue watching).
+  continueWatching: MediaItem[];
+  // Recently added movies in the library.
+  recentlyAdded: MediaItem[];
+  // One slider per genre (top genres by movie count).
+  genreRows: GenreRow[];
+  // Mix used for the hero banner.
+  heroItems: MediaItem[];
+  isLoading: boolean;
+  error: string | null;
+}
+
+const SECTION_LIMIT = 16;
+// How many genre sliders to show, and how many genres to probe to find them.
+const MAX_GENRE_ROWS = 8;
+const MAX_GENRES_PROBED = 20;
+
+function createMoviesStore() {
+  const initialState: MoviesState = {
+    continueWatching: [],
+    recentlyAdded: [],
+    genreRows: [],
+    heroItems: [],
+    isLoading: false,
+    error: null,
+  };
+
+  const { subscribe, set, update } = writable<MoviesState>(initialState);
+
+  /**
+   * Build the hero rotation. Prefer in-progress movies (most personal), then
+   * fall back to recently added. De-duplicates by id and prefers items that
+   * carry backdrop/primary artwork for a good banner.
+   */
+  function buildHero(continueWatching: MediaItem[], recentlyAdded: MediaItem[]): MediaItem[] {
+    const hasArt = (i: MediaItem) =>
+      !!(i.backdropImageTags && i.backdropImageTags.length > 0) || !!i.primaryImageTag;
+
+    const result: MediaItem[] = [];
+    const seen = new Set<string>();
+
+    for (const pool of [continueWatching, recentlyAdded]) {
+      for (const item of pool) {
+        if (result.length >= 6) break;
+        if (hasArt(item) && !seen.has(item.id)) {
+          seen.add(item.id);
+          result.push(item);
+        }
+      }
+    }
+
+    return result.slice(0, 6);
+  }
+
+  async function loadSections(libraryId: string) {
+    update(s => ({
+      ...s,
+      isLoading: s.continueWatching.length === 0 && s.recentlyAdded.length === 0,
+      error: null,
+    }));
+
+    try {
+      const repo = auth.getRepository();
+
+      const [resume, latest] = await Promise.all([
+        repo.getResumeMovies(SECTION_LIMIT),
+        repo.getLatestItems(libraryId, SECTION_LIMIT),
+      ]);
+
+      const heroItems = buildHero(resume, latest);
+
+      update(s => ({
+        ...s,
+        continueWatching: resume,
+        recentlyAdded: latest,
+        heroItems,
+        isLoading: false,
+      }));
+
+      // Genre rows are secondary — load them after the main sections paint so
+      // the page isn't blocked on N per-genre queries.
+      loadGenreRows(libraryId);
+    } catch (error) {
+      const message = error instanceof Error ? error.message : "Failed to load movie sections";
+      update(s => ({ ...s, isLoading: false, error: message }));
+      console.error("Failed to load movie sections:", error);
+    }
+  }
+
+  /**
+   * Build one slider per genre, showing the top-rated movies in each. We probe
+   * a bounded set of genres in parallel, drop empty ones, then keep the genres
+   * with the most movies (so niche/near-empty genres don't crowd the page).
+   */
+  async function loadGenreRows(libraryId: string) {
+    try {
+      const repo = auth.getRepository();
+      const genres = await repo.getGenres(libraryId);
+      if (genres.length === 0) return;
+
+      const probed = genres.slice(0, MAX_GENRES_PROBED);
+      const rows = await Promise.all(
+        probed.map(async (genre): Promise<GenreRow> => {
+          try {
+            const result = await repo.getItems(libraryId, {
+              includeItemTypes: ["Movie"],
+              genres: [genre.name],
+              sortBy: "CommunityRating",
+              sortOrder: "Descending",
+              recursive: true,
+              limit: SECTION_LIMIT,
+            });
+            return { id: genre.id, name: genre.name, items: result.items };
+          } catch (e) {
+            console.warn(`Failed to load genre row "${genre.name}":`, e);
+            return { id: genre.id, name: genre.name, items: [] };
+          }
+        })
+      );
+
+      const genreRows = rows
+        .filter(row => row.items.length > 0)
+        .sort((a, b) => b.items.length - a.items.length)
+        .slice(0, MAX_GENRE_ROWS);
+
+      update(s => ({ ...s, genreRows }));
+    } catch (e) {
+      console.warn("Failed to load movie genre rows:", e);
+    }
+  }
+
+  function reset() {
+    set(initialState);
+  }
+
+  return {
+    subscribe,
+    loadSections,
+    reset,
+  };
+}
+
+export const movies = createMoviesStore();
+
+export const moviesHeroItems = derived(movies, $m => $m.heroItems);
+export const isMoviesLoading = derived(movies, $m => $m.isLoading);