feat(monitoring): add Prometheus/Grafana monitoring stack

- Add Grafana dashboard service (port 3000)
- Add Prometheus time-series database (port 9090)
- Add PVE Exporter for Proxmox metrics (port 9221)
- Deploy on VM 101 (monitoring-docker) at 192.168.2.114
- Configure scraping for Proxmox node 192.168.2.100
- Add docker-compose configurations for all services
- Add template files for sensitive credentials (pve.yml.template, .env.template)

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

monitoring/prometheus/docker-compose.yml

@@ -0,0 +1,8 @@
+services:
+  prometheus:
+    image: prom/prometheus
+    volumes:
+      - "/home/server-admin/prometheus/prometheus.yml:/etc/prometheus/prometheus.yml"
+      - "/home/server-admin/prometheus/data:/prometheus"
+    ports:
+      - 9090:9090