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/deployment.yaml

@@ -48,6 +48,9 @@ spec:
             - name: rcon
               containerPort: 25575
               protocol: TCP
+            - name: metrics
+              containerPort: 9225
+              protocol: TCP
           env:
             - name: EULA
               value: "TRUE"