feat: real-time sync, notification & social system overhaul

- Add WS events: dm_channel_created, dm_channel_closed, friend_removed,
  channel_created/updated/deleted, server_updated
- Fix first-ever DM: broadcast dm_channel_created to recipient
- Add DELETE /api/dm/:id for closing DMs with re-open support
- Wire Close DM button in sidebar
- Fix dm_message_created for unknown channels (safety net)
- Broadcast friend_removed on friend deletion
- Sound system: track realtimeMessageEvents separately from API loads,
  play notification for messages in all channels, not just current
- Optimistic updates: send/edit/delete messages appear instantly with
  rollback on failure, temp message deduplication on WS echo
- Channel CRUD broadcasts to all server members
- Server update broadcast on PATCH
- Server join registers user in connectionManager immediately
- Reconnect: only reload current channel, preserve other channel caches
- Activity panel, right panel, member list toggle components

packages/web/src/App.tsx

@@ -44,14 +44,6 @@ export function App() {
           </ProtectedRoute>
         }
       />
-      <Route
-        path="/channels/@me/:channelId?"
-        element={
-          <ProtectedRoute>
-            <AppLayout />
-          </ProtectedRoute>
-        }
-      />
       <Route
         path="/join/:inviteCode"
         element={