docs: Add default credentials documentation for Grafana, Prometheus, and PostgreSQL

- Document default Grafana credentials: admin/admin
- Document Prometheus access without authentication
- Document PostgreSQL credentials: calejo/password
- Add security note to change default passwords after first login
- Update README.md and QUICK_START.md with credential information

QUICK_START.md

@@ -104,6 +104,32 @@ docker-compose up -d
 curl http://localhost:8080/health
 ```
 
+## 🔐 Default Credentials
+
+After deployment, use these credentials to access the services:
+
+### Grafana Dashboard
+- **URL**: http://localhost:3000 (or your server IP:3000)
+- **Username**: admin
+- **Password**: admin
+
+### Prometheus Metrics
+- **URL**: http://localhost:9091 (or your server IP:9091)
+- **Authentication**: None required by default
+
+### PostgreSQL Database
+- **Host**: localhost:5432
+- **Database**: calejo
+- **Username**: calejo
+- **Password**: password
+
+### Main Application
+- **Dashboard**: http://localhost:8080/dashboard
+- **API**: http://localhost:8080
+- **Authentication**: JWT-based (configure users through dashboard)
+
+**Security Note**: Change the default Grafana admin password after first login!
+
 ## 📞 Support
 
 - **Documentation**: Check the `docs/` directory for comprehensive guides

README.md

@@ -188,6 +188,18 @@ After setup, access the dashboard at `http://your-server:8080/dashboard` to conf
 
 ---
 
+### Default Credentials
+
+After deployment:
+- **Grafana Dashboard**: admin / admin (http://localhost:3000)
+- **Prometheus Metrics**: No authentication required (http://localhost:9091)
+- **PostgreSQL Database**: calejo / password (localhost:5432)
+- **Main Dashboard**: http://localhost:8080/dashboard
+
+**Security Note**: Change default passwords after first login!
+
+---
+
 ### Traditional Installation (Alternative)
 
 If you prefer manual setup: