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/adapter/input/http/rest/monitoring_handler.go

@@ -43,6 +43,12 @@ func (h *MonitoringHandler) GetClusterMonitoring(w http.ResponseWriter, r *http.
 	respondJSON(w, http.StatusOK, response)
 }
 
+// GetClusterStats is a compatibility alias for cluster detail dashboards that
+// historically read stats from /clusters/{id}/stats.
+func (h *MonitoringHandler) GetClusterStats(w http.ResponseWriter, r *http.Request) {
+	h.GetClusterMonitoring(w, r)
+}
+
 // ListClusterMonitoring 获取所有集群的监控信息
 // @Summary 列出集群监控
 // @Tags Monitoring