[FEATURE] - Add "remote downscale" option for remote control.

[bitbound]

When the viewer's canvas is smaller than the remote display's resolution, we're wasting bandwidth by sending a full-res image. The browser will downscale it for the canvas anyway.

Add an option for "remote downscaling". When enabled, the viewer will send the canvas size at the start of the session and whenever the size changes mid-session. If the device's resolution is greater than the canvas size, the device will downscale the image before sending it to reduce bandwidth utilization.

When enabled, we will also need to request a key frame when the canvas size changes.

[jibie]

This feature is absolutely amazing! It will significantly enhance bandwidth efficiency, especially on low-resolution canvases. I'm looking forward to seeing it implemented as soon as possible!