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/components/VoiceControls.tsx

@@ -5,10 +5,12 @@ export function VoiceControls() {
   const isDeafened = useVoiceStore((state) => state.isDeafened);
   const isVideoOn = useVoiceStore((state) => state.isVideoOn);
   const isScreenSharing = useVoiceStore((state) => state.isScreenSharing);
+  const noiseSuppression = useVoiceStore((state) => state.noiseSuppression);
   const toggleMute = useVoiceStore((state) => state.toggleMute);
   const toggleDeafen = useVoiceStore((state) => state.toggleDeafen);
   const toggleVideo = useVoiceStore((state) => state.toggleVideo);
   const toggleScreenShare = useVoiceStore((state) => state.toggleScreenShare);
+  const toggleNoiseSuppression = useVoiceStore((state) => state.toggleNoiseSuppression);
   const leaveVoice = useVoiceStore((state) => state.leaveVoice);
 
   return (
@@ -57,6 +59,17 @@ export function VoiceControls() {
       >
         [share]
       </button>
+      <button
+        onClick={toggleNoiseSuppression}
+        className={`px-1.5 py-0.5 rounded-sm transition-colors ${
+          noiseSuppression
+            ? 'text-gb-green bg-gb-bg-s border border-gb-green'
+            : 'text-gb-fg-s hover:text-gb-green hover:bg-gb-bg-t border border-transparent'
+        }`}
+        title={noiseSuppression ? 'Noise suppression on' : 'Noise suppression off'}
+      >
+        [ns{noiseSuppression ? '●' : '○'}]
+      </button>
       <div className="flex-1" />
       <button
         onClick={leaveVoice}