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/metrics_client.go

@@ -13,4 +13,7 @@ type MetricsClient interface {
 
 	// GetNodeMetrics 获取集群的节点指标
 	GetNodeMetrics(ctx context.Context, clusterID string) ([]*entity.NodeMetrics, error)
+
+	// GetPodResourceAllocations returns Pod requests/limits grouped by Pod.
+	GetPodResourceAllocations(ctx context.Context, clusterID string) ([]*entity.PodResourceAllocation, error)
 }