⚡️(frontend) use initial processor reference to avoid track recreation

Leverage reference to initial processor choice to prevent unnecessary
preview track recreation when updating processor options.

Improves performance by maintaining existing track instance during
processor updates instead of creating new tracks, eliminating visual
interruptions and reducing resource overhead.

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

@@ -146,10 +146,9 @@ export const Join = ({
       video: !!initialUserChoices.current &&
         initialUserChoices.current?.videoEnabled && {
           deviceId: initialUserChoices.current.videoDeviceId,
-          processor:
-            BackgroundProcessorFactory.deserializeProcessor(
-              processorSerialized
-            ),
+          processor: BackgroundProcessorFactory.deserializeProcessor(
+            initialUserChoices.current.processorSerialized
+          ),
         },
     },
     onError