feat: Implement Phase 2 dashboard for K8s agent system

Lightweight Go-based dashboard for Raspberry Pi cluster:

Backend:
- chi router with REST API
- Embedded static file serving
- JSON file-based state storage
- Health checks and CORS support

Frontend:
- Responsive dark theme UI
- Status view with nodes, alerts, ArgoCD apps
- Pending actions with approve/reject
- Action history and audit trail
- Workflow listing and manual triggers

Deployment:
- Multi-stage Dockerfile (small Alpine image)
- Kubernetes manifests with Pi 3 tolerations
- Resource limits: 32-64Mi memory, 10-100m CPU
- ArgoCD application manifest
- Kustomize configuration

API endpoints:
- GET /api/status - Cluster status
- GET/POST /api/pending - Action management
- GET /api/history - Action audit trail
- GET/POST /api/workflows - Workflow management

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

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

dashboard/deploy/deployment.yaml

@@ -0,0 +1,90 @@
+apiVersion: apps/v1
+kind: Deployment
+metadata:
+  name: k8s-agent-dashboard
+  namespace: k8s-agent
+  labels:
+    app.kubernetes.io/name: k8s-agent-dashboard
+    app.kubernetes.io/component: dashboard
+spec:
+  replicas: 1
+  selector:
+    matchLabels:
+      app.kubernetes.io/name: k8s-agent-dashboard
+  template:
+    metadata:
+      labels:
+        app.kubernetes.io/name: k8s-agent-dashboard
+    spec:
+      # Target Pi 3 node (lightweight workload)
+      tolerations:
+        - key: "node-type"
+          operator: "Equal"
+          value: "pi3"
+          effect: "NoSchedule"
+      nodeSelector:
+        kubernetes.io/arch: arm64
+
+      # Security context
+      securityContext:
+        runAsNonRoot: true
+        runAsUser: 1000
+        fsGroup: 1000
+
+      containers:
+        - name: dashboard
+          image: ghcr.io/will/k8s-agent-dashboard:latest
+          imagePullPolicy: Always
+          ports:
+            - name: http
+              containerPort: 8080
+              protocol: TCP
+          args:
+            - "--port"
+            - "8080"
+            - "--data"
+            - "/data"
+
+          # Resource limits for Pi 3 (1GB RAM)
+          resources:
+            requests:
+              memory: "32Mi"
+              cpu: "10m"
+            limits:
+              memory: "64Mi"
+              cpu: "100m"
+
+          # Health checks
+          livenessProbe:
+            httpGet:
+              path: /api/health
+              port: http
+            initialDelaySeconds: 5
+            periodSeconds: 30
+            timeoutSeconds: 3
+
+          readinessProbe:
+            httpGet:
+              path: /api/health
+              port: http
+            initialDelaySeconds: 3
+            periodSeconds: 10
+            timeoutSeconds: 3
+
+          # Volume mount for persistent data
+          volumeMounts:
+            - name: data
+              mountPath: /data
+
+          # Security
+          securityContext:
+            allowPrivilegeEscalation: false
+            readOnlyRootFilesystem: true
+            capabilities:
+              drop:
+                - ALL
+
+      volumes:
+        - name: data
+          persistentVolumeClaim:
+            claimName: k8s-agent-dashboard-data