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/argocd-application.yaml

@@ -0,0 +1,45 @@
+apiVersion: argoproj.io/v1alpha1
+kind: Application
+metadata:
+  name: k8s-agent-dashboard
+  namespace: argocd
+  labels:
+    app.kubernetes.io/name: k8s-agent-dashboard
+    app.kubernetes.io/part-of: k8s-agent-system
+  finalizers:
+    - resources-finalizer.argocd.argoproj.io
+spec:
+  project: default
+
+  source:
+    # Update this to your GitOps repo
+    repoURL: https://gitea.example.com/user/gitops-repo.git
+    targetRevision: HEAD
+    path: apps/k8s-agent-dashboard
+
+  destination:
+    server: https://kubernetes.default.svc
+    namespace: k8s-agent
+
+  syncPolicy:
+    automated:
+      prune: true
+      selfHeal: true
+      allowEmpty: false
+    syncOptions:
+      - CreateNamespace=true
+      - PrunePropagationPolicy=foreground
+      - PruneLast=true
+    retry:
+      limit: 5
+      backoff:
+        duration: 5s
+        factor: 2
+        maxDuration: 3m
+
+  # Health checks
+  ignoreDifferences:
+    - group: apps
+      kind: Deployment
+      jsonPointers:
+        - /spec/replicas