🐛 | Fix prefetch bug (str vs int), move json import to module level, add missing type hints

music_db.py

@@ -1,5 +1,6 @@
 """SQLite-backed database for song history, favourites, and play stats."""
 
+import json
 import sqlite3
 import threading
 from datetime import datetime, timezone
@@ -87,7 +88,6 @@ class MusicDB:
                     duration: int = 0,
                     thumbnail: Optional[str] = None) -> None:
         """Record that a song was played (upsert + history row)."""
-        import json
         artists_json = json.dumps(artists, ensure_ascii=False)
         album_json = json.dumps(album) if album else None
         with self._lock: