feat(db): cascade-cleanup queries for M7 #372 track removal

DeleteTrack returns album_id + artist_id so the calling service can
chain the album-empty / artist-empty cascade. DeleteAlbumIfEmpty and
DeleteArtistIfEmpty are no-ops when other rows still reference the
parent — the service treats pgx.ErrNoRows as "not orphaned, skip".

internal/db/dbq/tracks.sql.go

@@ -69,6 +69,37 @@ func (q *Queries) CountTracksMatchingForUser(ctx context.Context, arg CountTrack
 	return count, err
 }
 
+const deleteTrack = `-- name: DeleteTrack :one
+DELETE FROM tracks WHERE id = $1
+RETURNING id, album_id, artist_id, file_path, mbid
+`
+
+type DeleteTrackRow struct {
+	ID       pgtype.UUID
+	AlbumID  pgtype.UUID
+	ArtistID pgtype.UUID
+	FilePath string
+	Mbid     *string
+}
+
+// M7 #372: hard delete with FK cascade. The CASCADE on track_id from
+// play_events / general_likes_tracks / lidarr_quarantine /
+// lidarr_quarantine_actions handles their cleanup. RETURNING gives us
+// album_id + artist_id for the album-empty / artist-empty cascade
+// checks the service does next.
+func (q *Queries) DeleteTrack(ctx context.Context, id pgtype.UUID) (DeleteTrackRow, error) {
+	row := q.db.QueryRow(ctx, deleteTrack, id)
+	var i DeleteTrackRow
+	err := row.Scan(
+		&i.ID,
+		&i.AlbumID,
+		&i.ArtistID,
+		&i.FilePath,
+		&i.Mbid,
+	)
+	return i, err
+}
+
 const getTrackByID = `-- name: GetTrackByID :one
 SELECT id, title, album_id, artist_id, track_number, disc_number, duration_ms, file_path, file_size, file_format, bitrate, mbid, genre, added_at, updated_at FROM tracks WHERE id = $1
 `