feat(minecraft): add Prometheus metrics + Grafana dashboard

- minecraft-prometheus-exporter v3.1.2 plugin (port 9225)
- ServiceMonitor for Prometheus scraping
- Grafana dashboard ConfigMap (ID 20659, Minecraft server stats)
- metrics port added to Service and Deployment containerPorts

cluster/applications/minecraft/service.yaml

@@ -33,3 +33,7 @@ spec:
       port: 25575
       targetPort: 25575
       protocol: TCP
+    - name: metrics
+      port: 9225
+      targetPort: 9225
+      protocol: TCP