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/lib/player/localSource.ts

@@ -0,0 +1,49 @@
+/**
+ * Choosing between a downloaded file and a server stream for video playback.
+ *
+ * Audio has preferred local files since the queue is built (the Rust queue
+ * resolves `MediaSource::Local`), but video asks the repository for a stream URL
+ * and never consults `downloads` — so a downloaded film was streamed anyway,
+ * spending bandwidth that had already been spent and failing outright offline.
+ *
+ * Pure so it can be unit-tested: the component only supplies the two inputs and
+ * the asset-URL converter.
+ *
+ * TRACES: UR-071 | DR-123 | UT-118
+ */
+
+export interface VideoSourceInputs {
+  /** Absolute on-disk path of a completed download, or null to stream. */
+  localPath: string | null;
+  /** Stream URL the repository resolved (already transcoded if it had to be). */
+  remoteUrl: string;
+  /** Whether the *remote* stream is a transcode. */
+  remoteNeedsTranscoding: boolean;
+  /** Usually Tauri's `convertFileSrc`; injected so this module stays pure. */
+  toAssetUrl: (path: string) => string;
+}
+
+export interface VideoSourceDecision {
+  /** What to hand the `<video>` element. */
+  url: string;
+  /**
+   * Local files are never transcodes, so this is always false for them. It
+   * matters because the transcoded path re-requests a whole new stream URL on
+   * every seek; a local file seeks natively and must not go down that route.
+   */
+  needsTranscoding: boolean;
+  /** True when playing from disk — for logging and the offline badge. */
+  isLocal: boolean;
+}
+
+export function resolveVideoSource(inputs: VideoSourceInputs): VideoSourceDecision {
+  const { localPath, remoteUrl, remoteNeedsTranscoding, toAssetUrl } = inputs;
+
+  // Treat blank/whitespace paths as absent — a malformed `downloads` row must
+  // not produce an asset URL pointing at nothing.
+  if (localPath && localPath.trim() !== "") {
+    return { url: toAssetUrl(localPath), needsTranscoding: false, isLocal: true };
+  }
+
+  return { url: remoteUrl, needsTranscoding: remoteNeedsTranscoding, isLocal: false };
+}