feat(frontend): add Helm chart browser, monitoring, chart-references and values templates pages

Add new frontend pages for the multi-tenant OCDP platform:

- Charts page (/charts): Browse Harbor OCI registries to list Helm chart repositories
  and versions, with deploy modal to launch charts on selected clusters
- Monitoring page (/monitoring): Display cluster metrics (CPU/Memory/GPU usage)
  and per-node details with resource utilization bars
- Chart References page (/chart-references): CRUD for chart metadata references
- Values Templates page (/templates): CRUD for Helm values templates with version
  history and rollback support
- Sidebar: Add Charts navigation, update Storage and Templates links
- api.ts: Add all API client functions (clusterApi, registryApi, instanceApi,
  monitoringApi, storageApi, chartReferenceApi, valuesTemplateApi,
  workspaceApi, userApi) with full TypeScript types

Note: deploy flow and values template rollback not yet end-to-end tested.

backend/internal/domain/service/chart_reference_service.go

@@ -0,0 +1,137 @@
+package service
+
+import (
+	"context"
+	"errors"
+
+	"github.com/ocdp/cluster-service/internal/domain/entity"
+	"github.com/ocdp/cluster-service/internal/domain/repository"
+)
+
+var (
+	ErrChartReferenceNotFound = errors.New("chart reference not found")
+	ErrChartReferenceExists   = errors.New("chart reference already exists")
+)
+
+// ChartReferenceService Chart 引用领域服务
+type ChartReferenceService struct {
+	chartRefRepo repository.ChartReferenceRepository
+	registryRepo repository.RegistryRepository
+}
+
+// NewChartReferenceService 创建 Chart 引用服务
+func NewChartReferenceService(
+	chartRefRepo repository.ChartReferenceRepository,
+	registryRepo repository.RegistryRepository,
+) *ChartReferenceService {
+	return &ChartReferenceService{
+		chartRefRepo: chartRefRepo,
+		registryRepo: registryRepo,
+	}
+}
+
+// Create 创建 Chart 引用
+func (s *ChartReferenceService) Create(
+	ctx context.Context,
+	workspaceID, registryID, repository, chartName, description string,
+) (*entity.ChartReference, error) {
+	// 检查 Registry 是否存在
+	registry, err := s.registryRepo.GetByID(ctx, registryID)
+	if err != nil {
+		return nil, errors.New("registry not found")
+	}
+
+	// 检查名称是否已存在
+	existing, _ := s.chartRefRepo.GetByName(ctx, workspaceID, chartName)
+	if existing != nil {
+		return nil, ErrChartReferenceExists
+	}
+
+	chartRef := entity.NewChartReference(workspaceID, registry.ID, repository, chartName, description)
+	chartRef.Description = description
+
+	if err := s.chartRefRepo.Create(ctx, chartRef); err != nil {
+		return nil, err
+	}
+
+	return chartRef, nil
+}
+
+// GetByID 获取 Chart 引用
+func (s *ChartReferenceService) GetByID(ctx context.Context, id string) (*entity.ChartReference, error) {
+	chartRef, err := s.chartRefRepo.GetByID(ctx, id)
+	if err != nil {
+		return nil, ErrChartReferenceNotFound
+	}
+	return chartRef, nil
+}
+
+// GetByWorkspace 获取工作空间的所有 Chart 引用
+func (s *ChartReferenceService) GetByWorkspace(ctx context.Context, workspaceID string) ([]*entity.ChartReference, error) {
+	return s.chartRefRepo.GetByWorkspace(ctx, workspaceID)
+}
+
+// GetByRegistry 获取 Registry 的所有 Chart 引用
+func (s *ChartReferenceService) GetByRegistry(ctx context.Context, registryID string) ([]*entity.ChartReference, error) {
+	return s.chartRefRepo.GetByRegistry(ctx, registryID)
+}
+
+// Update 更新 Chart 引用
+func (s *ChartReferenceService) Update(
+	ctx context.Context,
+	id, registryID, repository, chartName, description string,
+	isEnabled bool,
+) (*entity.ChartReference, error) {
+	chartRef, err := s.chartRefRepo.GetByID(ctx, id)
+	if err != nil {
+		return nil, ErrChartReferenceNotFound
+	}
+
+	if registryID != "" {
+		chartRef.RegistryID = registryID
+	}
+	if repository != "" {
+		chartRef.Repository = repository
+	}
+	if chartName != "" {
+		chartRef.ChartName = chartName
+	}
+	chartRef.Description = description
+	chartRef.IsEnabled = isEnabled
+
+	if err := s.chartRefRepo.Update(ctx, chartRef); err != nil {
+		return nil, err
+	}
+
+	return chartRef, nil
+}
+
+// Delete 删除 Chart 引用
+func (s *ChartReferenceService) Delete(ctx context.Context, id string) error {
+	return s.chartRefRepo.Delete(ctx, id)
+}
+
+// List 列出所有 Chart 引用（管理员用）
+func (s *ChartReferenceService) List(ctx context.Context) ([]*entity.ChartReference, error) {
+	return s.chartRefRepo.List(ctx)
+}
+
+// Enable 启用 Chart 引用
+func (s *ChartReferenceService) Enable(ctx context.Context, id string) error {
+	chartRef, err := s.chartRefRepo.GetByID(ctx, id)
+	if err != nil {
+		return ErrChartReferenceNotFound
+	}
+	chartRef.IsEnabled = true
+	return s.chartRefRepo.Update(ctx, chartRef)
+}
+
+// Disable 禁用 Chart 引用
+func (s *ChartReferenceService) Disable(ctx context.Context, id string) error {
+	chartRef, err := s.chartRefRepo.GetByID(ctx, id)
+	if err != nil {
+		return ErrChartReferenceNotFound
+	}
+	chartRef.IsEnabled = false
+	return s.chartRefRepo.Update(ctx, chartRef)
+}