Add MJPEG fallback video transport and WebSocket input

[DjDeveloperr]

Summary

• Add a direct MJPEG-over-HTTP live video fallback alongside the existing WebRTC path.
• Add a WebSocket input channel for MJPEG sessions so touch and keyboard control still works when WebRTC is unavailable.
• Expose transport selection and stream settings in the browser UI, with docs and operator guidance updated to match.

Testing

• Ran client typecheck and unit tests.
• Built the production client bundle.
• Verified the local browser flow end to end, including MJPEG rendering, transport selection, and input control over WebSocket.