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/cmd/server/main.go

@@ -0,0 +1,81 @@
+package main
+
+import (
+	"embed"
+	"flag"
+	"io/fs"
+	"log"
+	"net/http"
+	"os"
+
+	"github.com/go-chi/chi/v5"
+	"github.com/go-chi/chi/v5/middleware"
+	"github.com/go-chi/cors"
+	"github.com/will/k8s-agent-dashboard/internal/api"
+	"github.com/will/k8s-agent-dashboard/internal/store"
+)
+
+//go:embed all:web
+var webFS embed.FS
+
+func main() {
+	port := flag.String("port", "8080", "Server port")
+	dataDir := flag.String("data", "/data", "Data directory for state")
+	flag.Parse()
+
+	// Initialize store
+	s, err := store.New(*dataDir)
+	if err != nil {
+		log.Fatalf("Failed to initialize store: %v", err)
+	}
+
+	// Create router
+	r := chi.NewRouter()
+
+	// Middleware
+	r.Use(middleware.Logger)
+	r.Use(middleware.Recoverer)
+	r.Use(middleware.Compress(5))
+	r.Use(cors.Handler(cors.Options{
+		AllowedOrigins:   []string{"*"},
+		AllowedMethods:   []string{"GET", "POST", "PUT", "DELETE", "OPTIONS"},
+		AllowedHeaders:   []string{"Accept", "Content-Type"},
+		ExposedHeaders:   []string{"Link"},
+		AllowCredentials: false,
+		MaxAge:           300,
+	}))
+
+	// API routes
+	r.Route("/api", func(r chi.Router) {
+		r.Get("/health", api.HealthCheck)
+		r.Get("/status", api.GetClusterStatus(s))
+		r.Get("/pending", api.GetPendingActions(s))
+		r.Post("/pending/{id}/approve", api.ApproveAction(s))
+		r.Post("/pending/{id}/reject", api.RejectAction(s))
+		r.Get("/history", api.GetActionHistory(s))
+		r.Get("/workflows", api.GetWorkflows(s))
+		r.Post("/workflows/{name}/run", api.RunWorkflow(s))
+	})
+
+	// Static files
+	webContent, err := fs.Sub(webFS, "web")
+	if err != nil {
+		log.Fatalf("Failed to get web content: %v", err)
+	}
+
+	fileServer := http.FileServer(http.FS(webContent))
+	r.Handle("/*", fileServer)
+
+	// Start server
+	addr := ":" + *port
+	if envPort := os.Getenv("PORT"); envPort != "" {
+		addr = ":" + envPort
+	}
+
+	log.Printf("Starting server on %s", addr)
+	log.Printf("Data directory: %s", *dataDir)
+
+	if err := http.ListenAndServe(addr, r); err != nil {
+		log.Fatalf("Server failed: %v", err)
+	}
+}