feat(phase6): video grid, noise suppression, whisper system

- New VideoGrid component: live camera feeds (local + remote) in VoicePanel
- Camera toggle in VoiceControls: enable/disable video per participant
- Noise suppression toggle in VoiceControls + voice store
- VOICE_WHISPER WS event: backend routes whisper to target user only
- Whisper UI: per-participant whisper button, notification toasts with dismiss
- Fix circular import between voice.ts and ws.ts (use lazy accessor)

web/src/stores/ws.ts

@@ -4,6 +4,7 @@ import { useChannelStore } from './channel.ts';
 import { useServerStore } from './server.ts';
 import { usePresenceStore } from './presence.ts';
 import { useTypingStore } from './typing.ts';
+import { useVoiceStore } from './voice.ts';
 import type { Message } from './message.ts';
 import type { Channel } from './channel.ts';
 import type { Server } from './server.ts';
@@ -176,6 +177,17 @@ export const useWebSocketStore = create<WebSocketState>((set, get) => ({
           }
           break;
         }
+        case 'VOICE_WHISPER': {
+          // Forwarded from backend — only intended recipient gets this
+          const { from_user_id, from_username, message } = data.payload as Record<string, string>;
+          useVoiceStore.getState()._addWhisper({
+            fromUserId: from_user_id || '',
+            fromUsername: from_username || 'unknown',
+            message: message || '',
+            timestamp: Date.now(),
+          });
+          break;
+        }
         default:
           break;
       }