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/server/src/routes/social.ts

@@ -279,6 +279,12 @@ export async function socialRoutes(app: FastifyInstance): Promise<void> {
       and(eq(schema.friends.userId, id), eq(schema.friends.friendId, request.userId))
     )).run();
 
+    // Broadcast friend_removed to the other user so their friends list updates
+    connectionManager.sendToUser(id, {
+      type: 'friend_removed',
+      userId: request.userId,
+    });
+
     return reply.code(200).send({ success: true });
   });