changed genre scanning to parse multiple genres, updated db to accommodate.

backend/database/sql/schemas/queue_tracks.sql

@@ -4,3 +4,6 @@ CREATE TABLE IF NOT EXISTS queue_tracks (
     position INTEGER NOT NULL,
     FOREIGN KEY(audio_file_id) REFERENCES audio_files(id) ON DELETE CASCADE
 );
+
+CREATE INDEX IF NOT EXISTS idx_queue_tracks_audio_file_id
+    ON queue_tracks(audio_file_id);