- SoundManager singleton wraps ma_engine + ma_sound (non-blocking, background thread) - MP3 files embedded in QRC, decoded to PCM at startup with MA_SOUND_FLAG_DECODE - miniaudio.h (MIT) in lib/, IMPLEMENTATION in separate miniaudio_impl.c - Sound settings page in SettingsDialog: enable/disable, volume slider (0-100%) - Config keys [gui] sound_enabled, sound_volume - Incoming messages trigger msg_incoming.mp3 sound