feat(monitoring): add smartctl, fail2ban, wireguard exporters and dashboards

- smartctl_exporter (disks), fail2ban exporter, wireguard exporter
- grafana dashboards for each exporter
- prometheus: firewall source rules, honor_labels/params scrape config
- node_exporter: zfs collector
- wireguard: nftables dep, resolvconf wrapper, reload fix
- remove superseded monitoring role

roles/grafana/files/node-exporter-dashboard.json

@@ -1,5 +1,5 @@
 {
-  "title": "Node Exporter - Host Overview",
+  "title": "Host Overview",
   "uid": "node-exporter-overview",
   "tags": ["node-exporter", "linux", "system"],
   "schemaVersion": 39,
@@ -107,7 +107,8 @@
       "targets": [
         { "refId": "A", "expr": "node_memory_MemTotal_bytes{instance=\"$instance\"} - node_memory_MemAvailable_bytes{instance=\"$instance\"}", "legendFormat": "Used" },
         { "refId": "B", "expr": "node_memory_Cached_bytes{instance=\"$instance\"} + node_memory_Buffers_bytes{instance=\"$instance\"}", "legendFormat": "Cached+Buffers" },
-        { "refId": "C", "expr": "node_memory_MemAvailable_bytes{instance=\"$instance\"}", "legendFormat": "Available" }
+        { "refId": "C", "expr": "node_memory_MemAvailable_bytes{instance=\"$instance\"}", "legendFormat": "Available" },
+        { "refId": "D", "expr": "node_zfs_arc_size{instance=\"$instance\"}", "legendFormat": "ZFS ARC" }
       ]
     },
     {