⚡️(frontend) optimize enterRoom calls in useWaitingParticipants

Replace sequential await inside the loop with Promise.all, since
each enterRoom call is independent.

This prevents unnecessary delays when multiple participants are
waiting (e.g. 10 participants previously resulted in ~10x longer
execution time).

src/frontend/src/features/rooms/hooks/useWaitingParticipants.ts

@@ -74,13 +74,17 @@ export const useWaitingParticipants = () => {
   ): Promise<void> => {
     try {
       setListEnabled(false)
-      for (const participant of waitingParticipants) {
-        await enterRoom({
-          roomId: roomId,
-          allowEntry,
-          participantId: participant.id,
-        })
-      }
+
+      await Promise.all(
+        waitingParticipants.map((participant) =>
+          enterRoom({
+            roomId: roomId,
+            allowEntry,
+            participantId: participant.id,
+          })
+        )
+      )
+
       await refetchWaiting()
     } catch (e) {
       console.error(e)