- Create src/audio/sounds.ts with playCorrectSound, playRewardSound, playForestElementSound
- Create src/audio/speech.ts with speakText via Web Speech API
- Add speechEnabled field to Settings interface in types.ts
- Add speechEnabled defaults in all Settings initializers (gemini.ts, parent.ts, db.test.ts)
- All sound functions check audioEnabled, speakText checks speechEnabled
- AudioContext lazy initialization for autoplay policy compliance
