feat: add iOS local recording controls

[zkewal]

Summary

Add an iOS-only public API for explicitly starting and stopping local microphone recording before publish/connect. The native bridge now emits LK_AUDIO_RECORDING_STATE, giving apps a concrete recording boundary they can use for "talk now" UX instead of inferring readiness from earlier setup.

Changes

JS API surface

• add AudioSession.startLocalRecording() and AudioSession.stopLocalRecording()
• register LK_AUDIO_RECORDING_STATE in the JS native event registry
• add unit coverage for method delegation and event registration

iOS bridge and recording control

• expose startLocalRecording and stopLocalRecording through LivekitReactNativeModule
• emit local_recording_start_requested, local_recording_started, local_recording_start_failed, and local_recording_stopped
• add LKAudioProcessingManager wrappers that start and stop recording through WebRTC's audioDeviceModule

Cleanup

• remove leftover NSLog output from AudioSinkRenderer

Testing & Validation

• yarn test src/audio/AudioSession.test.ts --runInBand
• ./node_modules/.bin/tsc --noemit -p tsconfig.build.json
• ./node_modules/.bin/eslint src/audio/AudioSession.ts src/audio/AudioSession.test.ts src/audio/MediaRecorder.ts src/events/EventEmitter.ts --max-warnings 0
• yarn prepare
• xcodebuild -project ios/LivekitReactNative.xcodeproj -scheme LivekitReactNative -configuration Debug -sdk iphonesimulator build CODE_SIGNING_ALLOWED=NO

Notes for Reviewers

• iOS-only change; this PR does not add Android behavior.
• This builds on feat: preconnect audio buffer #256 (feat: preconnect audio buffer) by exposing a product-facing recording boundary rather than relying on earlier recorder setup state.

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[zkewal]

@davidliu can you review this 🙌