🔧(frontend) enable adaptive stream optimizations

Adaptive stream is a key optimization in large room.

Enabled adaptive stream to automatically manage
the quality of subscribed video tracks, optimizing
for bandwidth and CPU usage.

When video elements are visible, it adjusts
the resolution based on the size of the largest visible
element. If no video elements are visible, it
temporarily pauses the track until they are visible again.

Additionally, introduced support for custom pixel density,
which defaults to `2` for high-density screens
(devicePixelRatio ≥ 3) or `1` for standard screens.
Setting it to `screen` allows the pixel density to match
the actual screen's devicePixelRatio, optimizing video
clarity on ultra-high-definition displays.

This ensures a balance between streaming quality
and resource consumption.

This might also significantly increase the bandwidth
consumed by people streaming on high definition screens.
It needs to be battle tested.

OpenTalk uses a adaptiveStream equals true, while LiveKit
demo app uses 'screen' value. I followed OpenTalk choice,
I was scared 'screen' value creates performance issues
for user with high resolution screen in poor network conditions.

src/frontend/src/features/rooms/components/Conference.tsx

@@ -65,6 +65,7 @@ export const Conference = ({
 
   const roomOptions = useMemo((): RoomOptions => {
     return {
+      adaptiveStream: true,
       publishDefaults: {
         videoCodec: 'vp9',
       },