monitoring: add Prometheus + Grafana stack (kube-prometheus-stack)

Deploys kube-prometheus-stack via helm-controller: Prometheus, Grafana (internal-only), node-exporter, kube-state-metrics. Adds prometheus-pve-exporter for Proxmox (token in an out-of-band Secret), scrape configs for external hosts (.48/.70/.71/.49), community dashboards (Node Exporter Full, Proxmox via Prometheus) and a custom Hardware Temperatures dashboard. Grafana liveness made tolerant for slow first-boot migrations.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

monitoring/grafana-temps-dashboard.yaml

@@ -0,0 +1,91 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: grafana-dashboard-temps
+  namespace: monitoring
+  labels:
+    grafana_dashboard: "1"
+data:
+  hardware-temperatures.json: |
+    {
+      "annotations": {"list": []},
+      "editable": true,
+      "graphTooltip": 0,
+      "links": [],
+      "panels": [
+        {
+          "datasource": {"type": "prometheus", "uid": "${datasource}"},
+          "fieldConfig": {
+            "defaults": {
+              "color": {"mode": "thresholds"},
+              "unit": "celsius",
+              "thresholds": {"mode": "absolute", "steps": [
+                {"color": "green", "value": null},
+                {"color": "yellow", "value": 60},
+                {"color": "orange", "value": 75},
+                {"color": "red", "value": 85}
+              ]}
+            },
+            "overrides": []
+          },
+          "gridPos": {"h": 8, "w": 12, "x": 0, "y": 0},
+          "id": 1,
+          "options": {
+            "colorMode": "background",
+            "graphMode": "area",
+            "orientation": "auto",
+            "reduceOptions": {"calcs": ["lastNotNull"], "fields": "", "values": false},
+            "textMode": "auto"
+          },
+          "pluginVersion": "11.0.0",
+          "title": "Max temperature per host (now)",
+          "type": "stat",
+          "targets": [
+            {"datasource": {"type": "prometheus", "uid": "${datasource}"},
+             "expr": "max by (instance) (node_hwmon_temp_celsius)",
+             "legendFormat": "{{instance}}", "refId": "A"}
+          ]
+        },
+        {
+          "datasource": {"type": "prometheus", "uid": "${datasource}"},
+          "fieldConfig": {
+            "defaults": {
+              "color": {"mode": "palette-classic"},
+              "unit": "celsius",
+              "custom": {"drawStyle": "line", "lineWidth": 1, "fillOpacity": 10, "showPoints": "never"},
+              "thresholds": {"mode": "absolute", "steps": [
+                {"color": "green", "value": null},
+                {"color": "red", "value": 85}
+              ]}
+            },
+            "overrides": []
+          },
+          "gridPos": {"h": 8, "w": 12, "x": 12, "y": 0},
+          "id": 2,
+          "options": {
+            "legend": {"displayMode": "table", "placement": "bottom", "calcs": ["last", "max"]},
+            "tooltip": {"mode": "multi"}
+          },
+          "title": "All temperature sensors",
+          "type": "timeseries",
+          "targets": [
+            {"datasource": {"type": "prometheus", "uid": "${datasource}"},
+             "expr": "node_hwmon_temp_celsius",
+             "legendFormat": "{{instance}} / {{chip}} / {{sensor}}", "refId": "A"}
+          ]
+        }
+      ],
+      "refresh": "30s",
+      "schemaVersion": 39,
+      "tags": ["hardware", "temperature"],
+      "templating": {"list": [
+        {"current": {}, "hide": 0, "includeAll": false, "label": "Datasource",
+         "multi": false, "name": "datasource", "options": [], "query": "prometheus",
+         "refresh": 1, "type": "datasource"}
+      ]},
+      "time": {"from": "now-6h", "to": "now"},
+      "timezone": "Europe/Oslo",
+      "title": "Hardware Temperatures",
+      "uid": "hw-temps",
+      "version": 1
+    }