fix: FLAC, Ogg and Opus tracks carry their MusicBrainz recording id from the tag: one reader in library gives the scanner, the backfills and the importer the same ids, and the next scan re-reads the library (#5637)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/library/mbidbackfill.go

@@ -165,7 +165,8 @@ func readMBIDsForFile(path string, logger *slog.Logger) (albumMBID, artistMBID s
 		logger.Warn("mbid backfill: tag read failed", "path", path, "err", err)
 		return "", ""
 	}
-	return extractMBIDs(meta)
+	ids := ReadTagMBIDs(meta)
+	return ids.Release, ids.Artist
 }
 
 // BackfillTrackMBIDsResult tallies the track recording-MBID backfill.
@@ -258,5 +259,5 @@ func readRecordingMBIDForFile(path string, logger *slog.Logger) string {
 		logger.Warn("track mbid backfill: tag read failed", "path", path, "err", err)
 		return ""
 	}
-	return extractRecordingMBID(meta)
+	return ReadTagMBIDs(meta).Recording
 }