feat(search): answer search from a local index; tier downloads by lifetime

Search's instant leg read only downloaded items, so with no downloads it
returned nothing and every keystroke fell through to a full Recursive=true
server query. It now reads the whole synced catalog through the same
availability CTE get_items uses, gated on the same include_catalog_browse
flag so search and browse cannot diverge. (UR-065, DR-108)

Also fixes three defects found while confirming that:

- items_fts grew by a full duplicate index every catalog pass. INSERT OR
  REPLACE fires no AFTER DELETE trigger without recursive_triggers, so the
  old index row was orphaned, and a TEXT PRIMARY KEY meant the replacement
  took a fresh rowid and inserted a second entry. Now a real upsert, with
  migration 021 rebuilding existing indexes. (DR-110)
- DELETE FROM items existed nowhere, so server-side deletions never
  propagated. Adds a post-crawl mark-and-sweep, scoped to crawled types,
  skipping downloaded items, and refusing to run after a partial crawl
  because items.parent_id cascades. (DR-110)
- The index omitted MusicArtist, Playlist and People, which search groups
  results by. Adds them plus people_fts (migration 022). (DR-111)

Re-indexing moves from a frontend startup call to a Rust background task
with a 6h TTL, so a long session no longer searches a stale catalog and a
restart no longer forces a crawl regardless of freshness. (DR-109, IR-030)

Downloads gain a lifetime tier. Eviction selected every completed row by
age with no download_source filter, so hitting the storage limit deleted
the oldest download -- typically one saved deliberately for offline -- to
make room for a precached track. It now reclaims only 'auto' rows, and
expired ones are reclaimed first, before live cache is evicted.
(DR-126, DR-127)

Downloaded video and audio-only handoffs now play from disk instead of
streaming; the video path had never consulted downloads at all. No
transcode is involved: MPV runs video=no and ExoPlayer has no surface for
an Audio item. (DR-123 in part, DR-128)

FTS queries are built as quoted phrases so apostrophes, hyphens and
slashes are data rather than operator syntax, and the item-type filter is
bound rather than interpolated.

Specs: docs/specs/catalog-index-search.md,
docs/specs/read-through-media-cache.md

Includes concurrently-developed favourites browsing and background-audio
stream-end handling; the two workstreams share offline.rs, lib.rs and
online.rs, so no subset of files builds independently.

src/routes/+page.svelte

@@ -133,6 +133,11 @@
   const nextUpItems = $derived($home.nextUpItems);
   const latestItems = $derived($home.latestItems);
   const recentlyPlayedAudio = $derived($home.recentlyPlayedAudio);
+  // Favourite rows. Each is hidden when empty, so a fresh install shows none.
+  // TRACES: UR-067 | DR-118
+  const favoriteMovies = $derived($home.favoriteMovies);
+  const favoriteShows = $derived($home.favoriteShows);
+  const favoriteMusic = $derived($home.favoriteMusic);
   const resumeMovies = $derived($home.resumeMovies);
   const isLoading = $derived($home.isLoading);
 </script>
@@ -218,6 +223,39 @@
       />
     {/if}
 
+    <!-- Favourites. Hidden entirely when a category has nothing in it —
+         empty rows on a fresh install read as broken. ux-flows §5C.2.
+         TRACES: UR-067 | DR-118 -->
+    {#if favoriteMovies.length > 0}
+      <Carousel
+        title="Favourite Movies"
+        items={favoriteMovies}
+        onItemClick={handleItemClick}
+        onItemLongPress={handleItemLongPress}
+        showAll={() => goto("/library/favorites?scope=movies")}
+      />
+    {/if}
+
+    {#if favoriteShows.length > 0}
+      <Carousel
+        title="Favourite Shows"
+        items={favoriteShows}
+        onItemClick={handleItemClick}
+        onItemLongPress={handleItemLongPress}
+        showAll={() => goto("/library/favorites?scope=tv")}
+      />
+    {/if}
+
+    {#if favoriteMusic.length > 0}
+      <Carousel
+        title="Favourite Music"
+        items={favoriteMusic}
+        onItemClick={handleItemClick}
+        onItemLongPress={handleItemLongPress}
+        showAll={() => goto("/library/favorites?scope=music")}
+      />
+    {/if}
+
     <!-- Quick Access -->
     <div class="pt-4 px-4">
       <button