feat(demo): add Grafana dashboard and populate empty config directories

- Add Grafana Docker Infrastructure Overview dashboard (CPU, memory,
  container count, image count panels querying InfluxDB)
- Move dashboard JSON to config/grafana/dashboards/ for proper
  provisioning by Grafana's file provider
- Add .gitkeep to 10 empty config directories (pihole, drawio, kroki,
  atomictracker, archivebox, tubearchivist, wakapi, mailhog,
  influxdb, atuin) so git tracks the directory structure

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Assisted-by: GLM-5.1 via Crush <crush@charm.land>

demo/config/grafana/dashboards/docker-overview.json

@@ -0,0 +1,229 @@
+{
+  "annotations": {
+    "list": [
+      {
+        "builtIn": 1,
+        "datasource": "-- Grafana --",
+        "enable": true,
+        "hide": true,
+        "iconColor": "rgba(0, 211, 255, 1)",
+        "name": "Annotations & Alerts",
+        "type": "dashboard"
+      }
+    ]
+  },
+  "description": "Docker container resource monitoring via InfluxDB",
+  "editable": true,
+  "fiscalYearStartMonth": 0,
+  "graphTooltip": 0,
+  "id": null,
+  "links": [],
+  "panels": [
+    {
+      "datasource": "InfluxDB",
+      "fieldConfig": {
+        "defaults": {
+          "color": {
+            "mode": "palette-classic"
+          },
+          "custom": {
+            "axisBorderShow": false,
+            "axisCenteredZero": false,
+            "axisColorMode": "text",
+            "axisLabel": "",
+            "axisPlacement": "auto",
+            "barAlignment": 0,
+            "drawStyle": "line",
+            "fillOpacity": 10,
+            "gradientMode": "none",
+            "hideFrom": {
+              "legend": false,
+              "tooltip": false,
+              "viz": false
+            },
+            "lineInterpolation": "linear",
+            "lineWidth": 1,
+            "pointSize": 5,
+            "scaleDistribution": {
+              "type": "linear"
+            },
+            "showPoints": "auto",
+            "spanNulls": false,
+            "stacking": {
+              "group": "A",
+              "mode": "none"
+            },
+            "thresholdsStyle": {
+              "mode": "off"
+            }
+          },
+          "mappings": [],
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              { "color": "green", "value": null },
+              { "color": "red", "value": 80 }
+            ]
+          },
+          "unit": "percent"
+        },
+        "overrides": []
+      },
+      "gridPos": { "h": 8, "w": 12, "x": 0, "y": 0 },
+      "id": 1,
+      "options": {
+        "legend": { "calcs": [], "displayMode": "list", "placement": "bottom", "showLegend": true },
+        "tooltip": { "mode": "single", "sort": "none" }
+      },
+      "targets": [
+        {
+          "datasource": "InfluxDB",
+          "query": "from(bucket: \"demo_metrics\")\n  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)\n  |> filter(fn: (r) => r._measurement == \"docker_container_cpu\")\n  |> filter(fn: (r) => r._field == \"usage_percent\")",
+          "refId": "A"
+        }
+      ],
+      "title": "Container CPU Usage",
+      "type": "timeseries"
+    },
+    {
+      "datasource": "InfluxDB",
+      "fieldConfig": {
+        "defaults": {
+          "color": { "mode": "palette-classic" },
+          "custom": {
+            "axisBorderShow": false,
+            "axisCenteredZero": false,
+            "axisColorMode": "text",
+            "axisLabel": "",
+            "axisPlacement": "auto",
+            "barAlignment": 0,
+            "drawStyle": "line",
+            "fillOpacity": 10,
+            "gradientMode": "none",
+            "hideFrom": { "legend": false, "tooltip": false, "viz": false },
+            "lineInterpolation": "linear",
+            "lineWidth": 1,
+            "pointSize": 5,
+            "scaleDistribution": { "type": "linear" },
+            "showPoints": "auto",
+            "spanNulls": false,
+            "stacking": { "group": "A", "mode": "none" },
+            "thresholdsStyle": { "mode": "off" }
+          },
+          "mappings": [],
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              { "color": "green", "value": null },
+              { "color": "red", "value": 80 }
+            ]
+          },
+          "unit": "bytes"
+        },
+        "overrides": []
+      },
+      "gridPos": { "h": 8, "w": 12, "x": 12, "y": 0 },
+      "id": 2,
+      "options": {
+        "legend": { "calcs": [], "displayMode": "list", "placement": "bottom", "showLegend": true },
+        "tooltip": { "mode": "single", "sort": "none" }
+      },
+      "targets": [
+        {
+          "datasource": "InfluxDB",
+          "query": "from(bucket: \"demo_metrics\")\n  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)\n  |> filter(fn: (r) => r._measurement == \"docker_container_mem\")\n  |> filter(fn: (r) => r._field == \"usage\")",
+          "refId": "A"
+        }
+      ],
+      "title": "Container Memory Usage",
+      "type": "timeseries"
+    },
+    {
+      "datasource": "InfluxDB",
+      "fieldConfig": {
+        "defaults": {
+          "color": { "mode": "thresholds" },
+          "mappings": [],
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              { "color": "green", "value": null },
+              { "color": "yellow", "value": 10 },
+              { "color": "red", "value": 14 }
+            ]
+          },
+          "unit": "short"
+        },
+        "overrides": []
+      },
+      "gridPos": { "h": 4, "w": 6, "x": 0, "y": 8 },
+      "id": 3,
+      "options": {
+        "colorMode": "value",
+        "graphMode": "area",
+        "justifyMode": "auto",
+        "orientation": "auto",
+        "reduceOptions": { "calcs": ["lastNotNull"], "fields": "", "values": false },
+        "textMode": "auto"
+      },
+      "targets": [
+        {
+          "datasource": "InfluxDB",
+          "query": "from(bucket: \"demo_metrics\")\n  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)\n  |> filter(fn: (r) => r._measurement == \"docker\")\n  |> filter(fn: (r) => r._field == \"containers_running\")\n  |> last()",
+          "refId": "A"
+        }
+      ],
+      "title": "Running Containers",
+      "type": "stat"
+    },
+    {
+      "datasource": "InfluxDB",
+      "fieldConfig": {
+        "defaults": {
+          "color": { "mode": "thresholds" },
+          "mappings": [],
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              { "color": "green", "value": null },
+              { "color": "yellow", "value": 15 },
+              { "color": "red", "value": 20 }
+            ]
+          },
+          "unit": "short"
+        },
+        "overrides": []
+      },
+      "gridPos": { "h": 4, "w": 6, "x": 6, "y": 8 },
+      "id": 4,
+      "options": {
+        "colorMode": "value",
+        "graphMode": "area",
+        "justifyMode": "auto",
+        "orientation": "auto",
+        "reduceOptions": { "calcs": ["lastNotNull"], "fields": "", "values": false },
+        "textMode": "auto"
+      },
+      "targets": [
+        {
+          "datasource": "InfluxDB",
+          "query": "from(bucket: \"demo_metrics\")\n  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)\n  |> filter(fn: (r) => r._measurement == \"docker\")\n  |> filter(fn: (r) => r._field == \"images\")\n  |> last()",
+          "refId": "A"
+        }
+      ],
+      "title": "Docker Images",
+      "type": "stat"
+    }
+  ],
+  "refresh": "30s",
+  "schemaVersion": 38,
+  "style": "dark",
+  "tags": ["docker", "infrastructure"],
+  "templating": { "list": [] },
+  "time": { "from": "now-1h", "to": "now" },
+  "timepicker": {},
+  "timezone": "utc",
+  "title": "Docker Infrastructure Overview",
+  "uid": "docker-overview",
+  "version": 1
+}