Backfill MusicBrainz recording ID from Navidrome during database scan

Navidrome provides musicBrainzId on tracks — now captured during
database updates so the MusicBrainz enrichment worker can skip
tracks that already have an MBID.

Uses COALESCE on UPDATE to never overwrite existing enrichment data
with NULL (safe for Plex/Jellyfin which don't provide this field).

Inspired by PR #279 — fixed data loss bug in the original where
unconditional UPDATE would erase existing MBIDs.

core/navidrome_client.py

@@ -120,6 +120,7 @@ class NavidromeTrack:
 
         self._album_id = navidrome_data.get('albumId', '')
         self._artist_id = navidrome_data.get('artistId', '')
+        self.musicBrainzId = navidrome_data.get('musicBrainzId')
 
     def _parse_date(self, date_str: Optional[str]) -> Optional[datetime]:
         if not date_str:

database/music_database.py

@@ -4638,6 +4638,9 @@ class MusicDatabase:
                     except Exception:
                         pass
 
+                # Extract MusicBrainz recording ID from server if available (Navidrome provides this)
+                mbid = getattr(track_obj, 'musicBrainzId', None) or None
+
                 # Check if track already exists — UPDATE to preserve enrichment columns,
                 # INSERT only for genuinely new tracks
                 cursor.execute("SELECT 1 FROM tracks WHERE id = ? LIMIT 1", (track_id,))
@@ -4646,20 +4649,21 @@ class MusicDatabase:
                 if is_new_track:
                     cursor.execute("""
                         INSERT INTO tracks
-                        (id, album_id, artist_id, title, track_number, duration, file_path, bitrate, server_source, track_artist, updated_at)
-                        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, CURRENT_TIMESTAMP)
-                    """, (track_id, album_id, artist_id, title, track_number, duration, file_path, bitrate, server_source, track_artist))
+                        (id, album_id, artist_id, title, track_number, duration, file_path, bitrate, server_source, track_artist, musicbrainz_recording_id, updated_at)
+                        VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?, CURRENT_TIMESTAMP)
+                    """, (track_id, album_id, artist_id, title, track_number, duration, file_path, bitrate, server_source, track_artist, mbid))
                 else:
                     # Update server-provided fields only — preserves spotify_track_id, deezer_id,
-                    # isrc, bpm, musicbrainz IDs, and all other enrichment data
+                    # isrc, bpm, and all other enrichment data
                     cursor.execute("""
                         UPDATE tracks
                         SET album_id = ?, artist_id = ?, title = ?, track_number = ?,
                             duration = ?, file_path = ?, bitrate = ?, server_source = ?,
                             track_artist = COALESCE(?, track_artist),
+                            musicbrainz_recording_id = COALESCE(?, musicbrainz_recording_id),
                             updated_at = CURRENT_TIMESTAMP
                         WHERE id = ?
-                    """, (album_id, artist_id, title, track_number, duration, file_path, bitrate, server_source, track_artist, track_id))
+                    """, (album_id, artist_id, title, track_number, duration, file_path, bitrate, server_source, track_artist, mbid, track_id))
 
                 conn.commit()