feat: on-device speech recognition, navigation screen, session picker

- Replace audio recording + server-side Whisper with expo-speech-recognition
- Add navigate screen for iTerm2 remote control
- Add session picker modal for switching Claude sessions
- Restyle command bar with colored button backgrounds
- Add speech recognition and microphone permissions

	app.json	diff | view | blame | history
	app/chat.tsx	diff | view | blame | history
	app/navigate.tsx	diff | view | blame | history
	app/settings.tsx	diff | view | blame | history
	components/SessionPicker.tsx	diff | view | blame | history
	components/chat/CommandBar.tsx	diff | view | blame | history
	components/chat/InputBar.tsx	diff | view | blame | history
	components/chat/MessageBubble.tsx	diff | view | blame | history
	components/chat/VoiceButton.tsx	diff | view | blame | history
	contexts/ChatContext.tsx	diff | view | blame | history
	contexts/ConnectionContext.tsx	diff | view | blame | history
	package-lock.json	diff | view | blame | history
	package.json	diff | view | blame | history
	services/audio.ts	diff | view | blame | history
	types/index.ts	diff | view | blame | history