hold the last frame on screen while switching live streams

Switching streams in the single camera view blanked the player until the new stream played, because the old player unmounts in the same render and the hidden new player gave the card no height. The outgoing video's last frame is now drawn to a canvas before the remount and covers the gap until the new stream plays, and the card takes the camera's aspect ratio so it keeps its size while the video is hidden.

web/src/views/live/LiveCameraView.tsx

@@ -873,9 +873,12 @@ export default function LiveCameraView({
                   growClassName,
                 )}
                 ref={clickOverlayRef}
-                style={{
-                  aspectRatio: constrainedAspectRatio,
-                }}
+                style={
+                  {
+                    aspectRatio: constrainedAspectRatio,
+                    "--camera-aspect": cameraAspectRatio,
+                  } as React.CSSProperties
+                }
               >
                 {clickOverlay && overlaySize.width > 0 && (
                   <div
@@ -914,7 +917,10 @@ export default function LiveCameraView({
                 )}
                 <LivePlayer
                   key={camera.name}
-                  className={fullscreen ? "rounded-none" : ""}
+                  className={cn(
+                    "aspect-[var(--camera-aspect)]",
+                    fullscreen && "rounded-none",
+                  )}
                   windowVisible
                   showStillWithoutActivity={false}
                   alwaysShowCameraName={false}