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/server/src/ws/handler.ts

@@ -187,6 +187,7 @@ function buildReadyPayload(userId: string): {
   servers: ServerWithChannelsAndMembers[];
   dmChannels: DmChannel[];
   folders: ServerFolder[];
+  voiceStates: Record<string, string[]>;
 } {
   const db = getDb();