grafana: add dashboards and fix permissions

- Change default OIDC role from Viewer to Editor for Explore access
- Add declarative dashboard provisioning
- Add node-exporter dashboard (CPU, memory, disk, load, network, I/O)
- Add Loki logs dashboard with host/job filters

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

services/grafana/dashboards/logs.json

@@ -0,0 +1,85 @@
+{
+  "uid": "logs-homelab",
+  "title": "Logs - Homelab",
+  "tags": ["loki", "logs", "homelab"],
+  "timezone": "browser",
+  "schemaVersion": 39,
+  "version": 1,
+  "refresh": "30s",
+  "templating": {
+    "list": [
+      {
+        "name": "host",
+        "type": "query",
+        "datasource": {"type": "loki", "uid": "loki"},
+        "query": "label_values(host)",
+        "refresh": 2,
+        "includeAll": true,
+        "multi": false,
+        "current": {"text": "All", "value": "$__all"}
+      },
+      {
+        "name": "job",
+        "type": "query",
+        "datasource": {"type": "loki", "uid": "loki"},
+        "query": "label_values(job)",
+        "refresh": 2,
+        "includeAll": true,
+        "multi": false,
+        "current": {"text": "All", "value": "$__all"}
+      },
+      {
+        "name": "search",
+        "type": "textbox",
+        "current": {"text": "", "value": ""},
+        "label": "Search"
+      }
+    ]
+  },
+  "panels": [
+    {
+      "id": 1,
+      "title": "Log Volume",
+      "type": "timeseries",
+      "gridPos": {"h": 6, "w": 24, "x": 0, "y": 0},
+      "datasource": {"type": "loki", "uid": "loki"},
+      "targets": [
+        {
+          "expr": "sum by (host) (count_over_time({host=~\"$host\", job=~\"$job\"} |~ \"$search\" [1m]))",
+          "legendFormat": "{{host}}",
+          "refId": "A"
+        }
+      ],
+      "fieldConfig": {
+        "defaults": {
+          "unit": "short"
+        }
+      },
+      "options": {
+        "legend": {"displayMode": "list", "placement": "bottom"}
+      }
+    },
+    {
+      "id": 2,
+      "title": "Logs",
+      "type": "logs",
+      "gridPos": {"h": 18, "w": 24, "x": 0, "y": 6},
+      "datasource": {"type": "loki", "uid": "loki"},
+      "targets": [
+        {
+          "expr": "{host=~\"$host\", job=~\"$job\"} |~ \"$search\"",
+          "refId": "A"
+        }
+      ],
+      "options": {
+        "showTime": true,
+        "showLabels": true,
+        "showCommonLabels": false,
+        "wrapLogMessage": true,
+        "prettifyLogMessage": false,
+        "enableLogDetails": true,
+        "sortOrder": "Descending"
+      }
+    }
+  ]
+}