feat: 重构监控中心导航，新增资源监控4大模块

- 主菜单「监控告警」→「监控中心」
- 「告警中心」→「告警服务」移至链路追踪下方
- 新增资源监控 Tab 页（主机/中间件/SNMP/站点拨测）
- Agent 新增网络采集器(network)和磁盘IO采集器(diskio)
- 后端扩展 Agent 上报模型，支持 NetworkStat/DiskIOStat
- 前端 ServerTableRow 展示网络和磁盘IO实时指标
- WebSocket MetricsUpdate 推送扩展

frontend/src/App.tsx

@@ -31,8 +31,7 @@ import { AIPredictiveAnalytics } from '@/components/aiops/AIPredictiveAnalytics'
 import AlertCenter from '@/components/monitor/alert-center/AlertCenter';
 import TraceManager from '@/components/monitor/trace/TraceManager';
 import GrafanaDashboard from '@/components/monitor/dashboard/GrafanaDashboard';
-import { AgentMonitor } from '@/components/agent/AgentMonitor';
-import { AgentAlerts } from '@/components/agent/AgentAlerts';
+import { MonitorCenter } from '@/pages/MonitorCenter';
 
 const queryClient = new QueryClient({
   defaultOptions: {
@@ -59,7 +58,8 @@ function App() {
             <Route path="regions" element={<RegionManager />} />
             <Route path="platforms" element={<PlatformManager />} />
             <Route path="cloud-billing" element={<CloudBilling />} />
-            <Route path="agent-monitor" element={<AgentMonitor />} />
+            {/* 资源监控（Agent 指标 + 中间件 + SNMP + 拨测） */}
+            <Route path="monitor-center" element={<MonitorCenter />} />
             <Route path="clusters" element={<K8sClusters />} />
             <Route path="nodes" element={<K8sNodes />} />
             <Route path="workloads" element={<K8sWorkloads />} />
@@ -73,7 +73,6 @@ function App() {
             <Route path="alert-center" element={<AlertCenter />} />
             <Route path="trace" element={<TraceManager />} />
             <Route path="grafana" element={<GrafanaDashboard />} />
-            <Route path="agent-alerts" element={<AgentAlerts />} />
             <Route path="alerts" element={<AlertManager />} />
             <Route path="logs" element={<AlertManager />} />
             <Route path="approval" element={<ApprovalFlowManager />} />