🚨(frontend) fix warning component from uncontrolled to controlled

When the hand has never been raised yet, the value is undefined and
not false, which leads to a react aria warning.

It's a bad practice. Fix it.

src/frontend/src/features/rooms/livekit/hooks/useRaisedHand.ts

@@ -19,5 +19,5 @@ export function useRaisedHand({ participant }: useRaisedHandProps) {
     }
   }
 
-  return { isHandRaised: parsedMetadata.raised, toggleRaisedHand }
+  return { isHandRaised: parsedMetadata.raised || false, toggleRaisedHand }
 }