[Video] Bundle of minor tweaks (#4904)

* fix bg color

* unique video urls for debug

* improve controls slightly

* mute until fullscreen

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Co-authored-by: Samuel Newman <10959775+mozzius@users.noreply.github.com>

src/view/com/util/post-embeds/VideoPlayerContext.tsx

@@ -14,6 +14,7 @@ export function VideoPlayerProvider({
   // eslint-disable-next-line @typescript-eslint/no-shadow
   const player = useExpoVideoPlayer(source, player => {
     player.loop = true
+    player.muted = true
     player.play()
   })