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/db/migrate.ts

@@ -22,6 +22,19 @@ export function runMigrations(db: Database.Database): void {
       columns: [
         { name: 'permissions', type: 'TEXT' }
       ]
+    },
+    {
+      name: 'dm_messages',
+      columns: [
+        { name: 'edited_at', type: 'INTEGER' },
+        { name: 'reply_to_id', type: 'TEXT' }
+      ]
+    },
+    {
+      name: 'attachments',
+      columns: [
+        { name: 'dm_message_id', type: 'TEXT' }
+      ]
     }
   ];