debug: add HTTP upgrade event listener to diagnose WebSocket routing

handleConnection never fires despite browser getting open event.
Adding server-level upgrade listener to see if upgrades reach NestJS.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/src/main.ts

@@ -14,5 +14,11 @@ async function bootstrap() {
   });
   await app.listen(3000);
   console.log('Wraith backend running on port 3000');
+
+  // Debug: monitor WebSocket upgrades at the HTTP server level
+  const server = app.getHttpServer();
+  server.on('upgrade', (req: any, socket: any) => {
+    console.log(`[HTTP-UPGRADE] ${req.method} ${req.url} from ${req.headers.origin || 'unknown'}`);
+  });
 }
 bootstrap();