fix: resolve LiveKit voice/video stability issues

- Guard Disconnected/ConnectionStateChanged event handlers against stale rooms:
  old room events no longer nuke the new room's state (root cause of buttons
  failing, mute getting stuck, DUPLICATE_IDENTITY cascades)
- Reset media state (isMuted/isCameraOn/isScreenSharing) on connect to prevent
  desync after reconnects
- Add voiceStates to WS ready payload so users see who's in voice on page load
- Wire VoiceControls buttons to check getActiveRoom() before SDK calls
- Guard ChannelSidebar against re-joining the same voice channel
- Switch LIVEKIT_URL to wss://nova.ddns.net/livekit for HTTPS secure context
  (required for getUserMedia in Safari)

packages/web/src/stores/serverStore.js

@@ -75,6 +75,15 @@ export const useServerStore = create((set, get) => ({
             return { servers: [...state.servers, server] };
         });
     },
+    joinByCode: async (inviteCode) => {
+        const server = await api.servers.joinByCode(inviteCode);
+        set((state) => {
+            if (state.servers.find(s => s.id === server.id))
+                return state;
+            return { servers: [...state.servers, server] };
+        });
+        return server;
+    },
     generateInvite: async (serverId) => {
         const result = await api.servers.invite(serverId);
         return result.inviteCode;