Add reader rehearsal recording controls

[KSemenenko]

Goal\nAdd local rehearsal recording controls directly on the Teleprompter reader screen so users can record themselves while reading.\n\n## Scope\n- Add reader chrome controls for recording microphone-only or camera + microphone.\n- Device selectors must default to the camera and microphone selected in Settings.\n- Keep background media separate from capture: camera/video background is stage scenery, recording source is explicit capture input.\n- Show a live unobtrusive audio-level indicator while recording or armed so the user can confirm microphone input.\n- Persist or download the recorded file locally from the browser.\n- Extend media settings for browser/LiveKit-supported audio/video capture options such as echo cancellation, noise suppression, automatic gain control, voice isolation when available, channel count, sample rate, and sample size where supported.\n- Add browser/UI tests for mic-only recording, camera+mic recording, device defaults, audio meter visibility, and background-media separation.\n\n## Notes\nLiveKit JS exposes audio capture options that map to browser constraints including deviceId, echoCancellation, noiseSuppression, autoGainControl, voiceIsolation, channelCount, sampleRate, and sampleSize. The first implementation should keep local recording browser-first and align settings so the LiveKit path can reuse the same capture intent.\n