fix(monitoring): correct Flask backend URL in version panel

- Change port from 5000 to 8000 (gunicorn port)
- Change service name from monitoring-flask-backend to monitoring_flask_backend

Author: claude

config/grafana/dashboards/Self_Monitoring_Dashboard.json

@@ -96,7 +96,7 @@
           "root_selector": "",
           "source": "url",
           "type": "json",
-          "url": "http://flask-pgss-api:8000/version",
+          "url": "http://monitoring_flask_backend:8000/version",
           "url_options": {
             "method": "GET"
           },