feat: DM infrastructure overhaul + volume sliders + LiveKit dynamic URL

- Add DM edit/delete endpoints (REST + WebSocket)
- Add DM typing indicators with real-time broadcast
- Fix volume sliders to control LiveKit mic/speaker
- Fix Send Message button on user profile popout
- Add New DM modal with user search
- Fix message pagination (SQL cursor instead of in-memory)
- Guard optional attachments on DM messages
- Dynamic LiveKit URL from request Host header
- DM sidebar auto-sorts by most recent message

packages/web/src/stores/voiceStore.js

@@ -43,6 +43,18 @@ export const useVoiceStore = create((set, get) => ({
     toggleCamera: () => set((state) => ({ isCameraOn: !state.isCameraOn })),
     toggleScreenShare: () => set((state) => ({ isScreenSharing: !state.isScreenSharing })),
     getVoiceUsers: (channelId) => get().voiceUsers.get(channelId) ?? [],
+    clearAllVoiceUsers: () => set({ voiceUsers: new Map() }),
+    // Leave voice without wiping the voiceUsers map (so sidebar still shows others)
+    leaveVoice: () => set({
+        currentVoiceChannelId: null,
+        isMuted: false,
+        isDeafened: false,
+        isCameraOn: false,
+        isScreenSharing: false,
+        participants: [],
+        connectionError: null,
+        isLiveKitConnected: false,
+    }),
     reset: () => set({
         voiceUsers: new Map(),
         currentVoiceChannelId: null,