feat(k8s): M13 多集群资源对比看板 — GetMultiClusterComparison handler + ClusterComparePage (柱状图/雷达图/饼图/详细对比表)

frontend/src/components/layout/Sidebar.tsx

@@ -9,6 +9,7 @@ import {
   Menu, Network, CloudCog, Globe, MapPin, Key,
   Brain, Activity, BarChart3, GitBranch,
   Bot, AlertTriangle, Container, Boxes, Clock, Rocket,
+  Layers,
 } from 'lucide-react';
 import { Button } from '@/components/ui/button';
 import { ScrollArea } from '@/components/ui/scroll-area';
@@ -38,6 +39,7 @@ const menuItems: MenuItem[] = [
     id: 'kubernetes', name: 'Kubernetes', icon: Cloud,
     children: [
       { id: 'k8s-clusters', name: '集群列表', icon: Cloud, path: '/kubernetes' },
+      { id: 'k8s-compare', name: '多集群对比', icon: Layers, path: '/kubernetes/compare' },
       { id: 'k8s-nodes', name: '节点管理', icon: Cpu, path: '/nodes' },
       {
         id: 'k8s-workload', name: '工作负载', icon: Boxes,