playBackgroundMusic method
Plays looping background music (automatically preloads on first call).
Implementation
Future<void> playBackgroundMusic({int track = 1}) async {
// 1) Make sure all files are cached at least once
await _ensurePreloaded();
// 2) Configure looping and volume
await _bgmPlayer.setReleaseMode(ReleaseMode.loop);
await _bgmPlayer.setVolume(0.4);
// 3) Pick the right file and play from its cached path
final key = (track == 2) ? 'background02.flac' : 'background.wav';
final path = _cachedFiles[key]!;
await _bgmPlayer.play(DeviceFileSource(path));
}