fix(api): use server.listen instead of app.listen for WebSocket support

- server.ts: switch from app.listen() to server.listen() so WebSocket
  upgrade handler is on the same server as HTTP requests
- lobbyService: add host as first player on lobby creation
- ws-client: guard against reconnect when already connecting
- ws-provider: skip connect if already connected

apps/api/src/server.ts

@@ -9,6 +9,6 @@ const server = createServer(app);
 
 setupWebSocket(server);
 
-app.listen(PORT, () => {
+server.listen(PORT, () => {
   console.log(`Server listening on port ${PORT}`);
 });