feat: autotag scoring overhaul, dump-based explore index, and lyrics search

Consolidates in-progress work across autotag, explore, and library:

- autotag: beets/Picard-informed scoring engine — ID-first matching, VA
  handling, recommendation tiers, and a merged distance/rank cascade, with
  an eval harness for regression tracking.
- explore: offline MusicBrainz dump import/incremental refresh replaces the
  legacy tier crawl; index-first local search with fuzzy matching and a
  dedicated ranker; disk-free guards for dump downloads.
- library: artist-credit extraction and matching.
- lyrics: owned-library lyric search (FTS) with LRCLIB backfill.

Also: rewrite README to be user-focused, and migrate upstream to
git.ljones.me/yonlu/yellowjacket.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

backend/queue/persistence.go

@@ -237,7 +237,7 @@ func (q *Queue) lookupChunk(
 		return
 	}
 
-	rows, err := q.db.Queries.LookupTrackMetaByPaths(q.db.Ctx, paths)
+	rows, err := q.db.ReadQueries.LookupTrackMetaByPaths(q.db.Ctx, paths)
 	if err != nil {
 		q.logger.Error("Batch metadata lookup failed", "err", err)
 
@@ -415,7 +415,7 @@ func (q *Queue) RestoreState() {
 	defer q.mu.Unlock()
 
 	// Restore queue metadata.
-	state, err := q.db.Queries.GetQueueState(q.db.Ctx)
+	state, err := q.db.ReadQueries.GetQueueState(q.db.Ctx)
 	if err != nil {
 		q.logger.Error("Failed to load queue state", "err", err)
 
@@ -444,7 +444,7 @@ func (q *Queue) RestoreState() {
 	}
 
 	// Restore queue tracks.
-	rows, err := q.db.Queries.GetQueueTracks(q.db.Ctx)
+	rows, err := q.db.ReadQueries.GetQueueTracks(q.db.Ctx)
 	if err != nil {
 		q.logger.Error("Failed to load queue tracks", "err", err)