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-tauri/src/commands/download/mod.rs

@@ -270,6 +270,19 @@ pub async fn download_item(
         if !can_download {
             warn!("Storage limit reached. Attempting to free space...");
 
+            // Reclaim expired temporary entries first: they are dead weight, so
+            // freeing them may avoid evicting cache that is still within its
+            // life. Best-effort — a failure here just means eviction does more.
+            // TRACES: UR-071 | DR-127
+            match cache_arc
+                .reclaim_expired_async(&db_service, &user_id, &chrono::Utc::now().to_rfc3339())
+                .await
+            {
+                Ok(n) if n > 0 => info!("Reclaimed {} expired cache entries", n),
+                Ok(_) => {}
+                Err(e) => warn!("Expired-entry reclaim failed: {}", e),
+            }
+
             // Try to evict LRU items to make space
             match cache_arc
                 .evict_lru_async(&db_service, &user_id, size as u64)