✨(frontend) add speaker select component for audio output configuration

Introduce speaker selection component requested by users to allow audio
output device configuration before entering calls.

Enables users to test and configure their preferred audio output device
during prejoin setup, ensuring proper audio routing before call begins.
Improves user experience by preventing audio issues during meetings.

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

@@ -102,11 +102,15 @@ export const Conference = ({
       audioCaptureDefaults: {
         deviceId: userConfig.audioDeviceId ?? undefined,
       },
+      audioOutput: {
+        deviceId: userConfig.audioOutputDeviceId ?? undefined,
+      },
     }
     // do not rely on the userConfig object directly as its reference may change on every render
   }, [
     userConfig.videoDeviceId,
     userConfig.audioDeviceId,
+    userConfig.audioOutputDeviceId,
     isAdaptiveStreamSupported,
     isDynacastSupported,
   ])