fix: improve microphone handling and cleanup

- Use mono audio instead of stereo for microphone input
- Add cleanup to stop audio track on component unmount
- Explicitly set AudioTrack to nil when creation fails

ui/src/routes/devices.$id.tsx

@@ -620,7 +620,7 @@ export default function KvmIdRoute() {
             echoCancellation: true,
             noiseSuppression: true,
             autoGainControl: true,
-            channelCount: 2,
+            channelCount: 1,
           }
         }).then((stream) => {
           microphoneRequestInProgress.current = false;
@@ -652,6 +652,13 @@ export default function KvmIdRoute() {
         audioTransceiver.sender.replaceTrack(null);
       }
     }
+
+    // Cleanup on unmount or when dependencies change
+    return () => {
+      if (audioTransceiver?.sender.track) {
+        audioTransceiver.sender.track.stop();
+      }
+    };
   }, [microphoneEnabled, audioTransceiver, peerConnection, setMicrophoneEnabled]);
 
   // Cleanup effect

webrtc.go

@@ -332,6 +332,7 @@ func newSession(config SessionConfig) (*Session, error) {
 	)
 	if err != nil {
 		scopedLogger.Warn().Err(err).Msg("Failed to create AudioTrack (non-fatal)")
+		session.AudioTrack = nil
 	} else {
 		_, err = peerConnection.AddTransceiverFromTrack(session.AudioTrack, webrtc.RTPTransceiverInit{
 			Direction: webrtc.RTPTransceiverDirectionSendrecv,