fix(webrtc): add error handling and ui alerts for background processor initialization

web/src/stores/voice.ts

@@ -336,6 +336,7 @@ export const useVoiceStore = create<VoiceState>((set, get) => ({
     }
 
     if (processor) {
+      try {
         if (mode === 'disabled') {
           await processor.switchTo({ mode: 'disabled' });
         } else if (mode === 'background-blur') {
@@ -350,9 +351,15 @@ export const useVoiceStore = create<VoiceState>((set, get) => ({
         if (track && track.setProcessor) {
           await track.setProcessor(processor);
         }
-    }
-
         set({ bgMode: mode });
+      } catch (err) {
+        console.error('[voice] setBgMode failed:', err);
+        alert(`Failed to set background effect: ${err instanceof Error ? err.message : err}`);
+        set({ bgMode: 'disabled' });
+      }
+    } else {
+      set({ bgMode: mode });
+    }
   },
 
   toggleScreenShare: async () => {