Add ping endpoint for health check

backend/src/index.js

@@ -26,6 +26,7 @@ app.use(cors());
 app.use(express.json());
 
 // ─── Public routes (no auth required) ────────────────────────────────────────
+app.get('/api/ping', (req, res) => res.json({ ok: true }));
 app.use('/api/auth', authRouter);
 
 // ─── Protected routes (JWT required) ─────────────────────────────────────────