fix: scale replicas in response, K8s metrics client, quota precheck, auth tests

- Add GetMetrics method to MetricsClient interface and implement cluster metrics API
- Add QuotaPrecheck service for validating resource quotas before deployment
- Add auth DTO with role/permission models and auth handler tests
- Add instance diagnostics: mounted NFS volumes, labels, annotations in pod diagnostics
- Update workspace handler with GetWorkspace endpoint and shared-user list
- Fix monitoring handler to use correct service method name
- Add tail_lines fallback in instance handler for snake_case query params
- Update nginx config for SSE log streaming support (no buffering)
- Add comprehensive test coverage: auth_service_test, auth_handler_test,
  auth_dto_test, metrics_client_test, quota_precheck_test
- Update error messages for quota validation and instance operations
- ModifyModal: fix YAML lineWidth:0, modified keys summary, delta-only submit
- InstanceCard: correctly disable scale-minus when replicas <= 0
- SidebarLayout: add hover transition for sidebar items
- Update todo.md and lessons.md with latest fixes

backend/internal/domain/repository/helm_client.go

@@ -3,8 +3,21 @@ package repository
 import (
 	"context"
 	"github.com/ocdp/cluster-service/internal/domain/entity"
+	"k8s.io/apimachinery/pkg/api/resource"
 )
 
+type ResourceVector struct {
+	CPU         resource.Quantity
+	Memory      resource.Quantity
+	GPU         int64
+	GPUMemoryMB int64
+}
+
+type ResourceEstimate struct {
+	Requests ResourceVector
+	Limits   ResourceVector
+}
+
 // HelmClient Helm 客户端接口（Output Port）
 type HelmClient interface {
 	// Install 安装 Helm Chart
@@ -33,4 +46,7 @@ type HelmClient interface {
 
 	// GetChartDefaultValues 从 chart 包中读取默认 values
 	GetChartDefaultValues(chartPath string) (map[string]interface{}, error)
+
+	// EstimateInstanceResources renders an instance chart with final values and sums Pod template resources.
+	EstimateInstanceResources(ctx context.Context, cluster *entity.Cluster, instance *entity.Instance) (*ResourceEstimate, error)
 }