feat: 监控大屏 /grafana→/dashboards + Agent主机Top10默认面板

- 路由: /grafana → /dashboards (Sidebar + App.tsx)
- GrafanaDashboard 新增默认面板: Agent 主机监控 Top 10
  - CPU/Memory/Disk 使用率三列排行
  - 进度条颜色: >85%红 >60%黄 <60%绿
  - 🥇🥈🥉 emoji 前三名
  - 30s 自动刷新
- Prometheus/Zabbix/SkyWalking 需配置数据源后才可用

frontend/src/App.tsx

@@ -73,7 +73,7 @@ function App() {
             <Route path="metrics" element={<MetricsExplorer />} />
             <Route path="alert-center" element={<AlertCenter />} />
             <Route path="trace" element={<TraceManager />} />
-            <Route path="grafana" element={<GrafanaDashboard />} />
+            <Route path="dashboards" element={<GrafanaDashboard />} />
             <Route path="alerts" element={<AlertManager />} />
             <Route path="logs" element={<AlertManager />} />
             <Route path="approval" element={<ApprovalFlowManager />} />

frontend/src/components/layout/Sidebar.tsx

@@ -88,7 +88,7 @@ const menuItems: MenuItem[] = [
     children: [
       { id: 'monitor-center', name: '资源监控', icon: Activity, path: '/monitor-center' },
       { id: 'metrics', name: '指标监控', icon: Cpu, path: '/metrics' },
-      { id: 'grafana', name: '监控大屏', icon: Monitor, path: '/grafana' },
+      { id: 'grafana', name: '监控大屏', icon: Monitor, path: '/dashboards' },
       { id: 'trace', name: '链路追踪', icon: GitBranch, path: '/trace' },
       { id: 'alert-center', name: '告警服务', icon: Bell, path: '/alert-center' },
     ],

frontend/src/components/monitor/dashboard/GrafanaDashboard.tsx

@@ -2,7 +2,7 @@ import React, { useState, useEffect } from 'react';
 import {
   Monitor, Settings, Plus, Edit, Trash2, Copy, Eye, Download, RefreshCw,
   Maximize2, Minimize2, Save, X, ChevronDown, BarChart3, LineChart, PieChart,
-  Activity, Cpu, Database, Server, Globe, Zap, AlertTriangle, TrendingUp,
+  Activity, Cpu, Database, Server, Globe, Zap, AlertTriangle, TrendingUp, HardDrive,
   TrendingDown, Clock, Calendar, Filter, Search
 } from 'lucide-react';
 import { Button } from '@/components/ui/button';
@@ -23,6 +23,7 @@ import { toast } from 'sonner';
 import { useConfirm } from '@/components/ui/confirm-dialog';
 import { dashboardApi } from '@/services/api';
 import { GrafanaPanelContent } from './GrafanaPanelContent';
+import { http } from '@/services/http';
 
 interface Dashboard {
   id: string;
@@ -107,6 +108,38 @@ const GrafanaDashboard: React.FC = () => {
     url: ''
   });
 
+  // Agent 主机监控 — 默认面板
+  const [hostTop, setHostTop] = useState<any[]>([]);
+  useEffect(() => {
+    (async () => {
+      try {
+        const [cpu, mem, disk] = await Promise.all([
+          http.get('/metrics/top?metric=cpu&limit=10'),
+          http.get('/metrics/top?metric=memory&limit=10'),
+          http.get('/metrics/top?metric=disk&limit=10'),
+        ]);
+        setHostTop([
+          { name: 'CPU', data: Array.isArray(cpu) ? cpu : [], key: 'cpu_usage', unit: '%', icon: 'cpu' },
+          { name: '内存', data: Array.isArray(mem) ? mem : [], key: 'memory_usage', unit: '%', icon: 'mem' },
+          { name: '磁盘', data: Array.isArray(disk) ? disk : [], key: 'disk_usage', unit: '%', icon: 'disk' },
+        ]);
+      } catch { /* silent */ }
+    })();
+    const timer = setInterval(async () => {
+      try {
+        const cpu = await http.get('/metrics/top?metric=cpu&limit=10');
+        const mem = await http.get('/metrics/top?metric=memory&limit=10');
+        const disk = await http.get('/metrics/top?metric=disk&limit=10');
+        setHostTop([
+          { name: 'CPU', data: Array.isArray(cpu) ? cpu : [], key: 'cpu_usage', unit: '%', icon: 'cpu' },
+          { name: '内存', data: Array.isArray(mem) ? mem : [], key: 'memory_usage', unit: '%', icon: 'mem' },
+          { name: '磁盘', data: Array.isArray(disk) ? disk : [], key: 'disk_usage', unit: '%', icon: 'disk' },
+        ]);
+      } catch { /* silent */ }
+    }, 30000);
+    return () => clearInterval(timer);
+  }, []);
+
   useEffect(() => {
     fetchDashboards();
     fetchDatasources();
@@ -253,6 +286,62 @@ const GrafanaDashboard: React.FC = () => {
 
   return (
     <div className={`space-y-4 ${fullscreen ? 'fixed inset-0 z-50 bg-background p-4' : ''}`}>
+      {/* ===== 默认：Agent 主机监控面板 ===== */}
+      <Card className="bg-[var(--dg-bg-secondary)] border-emerald-500/20">
+        <CardHeader className="pb-2">
+          <div className="flex items-center gap-2">
+            <Activity className="h-5 w-5 text-emerald-400" />
+            <CardTitle className="text-base text-[var(--dg-text-primary)]">Agent 主机监控</CardTitle>
+            <Badge variant="outline" className="text-xs bg-emerald-500/10 text-emerald-400 border-emerald-500/30">默认</Badge>
+            <span className="text-xs text-[var(--dg-text-muted)] ml-auto">每 30s 刷新</span>
+          </div>
+        </CardHeader>
+        <CardContent className="pt-0">
+          {hostTop.length === 0 ? (
+            <div className="text-center py-8 text-[var(--dg-text-muted)]">
+              <Server className="h-8 w-8 mx-auto mb-2 text-slate-600" />
+              <p className="text-sm">暂无 Agent 上报数据</p>
+              <p className="text-xs mt-1">请确保至少一台主机安装了 AIOps Agent 并正常上报</p>
+            </div>
+          ) : (
+            <div className="grid grid-cols-1 lg:grid-cols-3 gap-4">
+              {hostTop.map((group: any) => (
+                <div key={group.name} className="bg-[var(--dg-bg-primary)] rounded-lg p-3 border border-[var(--dg-border)]">
+                  <div className="flex items-center gap-2 mb-2">
+                    {group.icon === 'cpu' && <Cpu className="h-4 w-4 text-red-400" />}
+                    {group.icon === 'mem' && <Server className="h-4 w-4 text-amber-400" />}
+                    {group.icon === 'disk' && <HardDrive className="h-4 w-4 text-orange-400" />}
+                    <span className="text-xs font-medium text-[var(--dg-text-primary)]">{group.name} Top 10</span>
+                  </div>
+                  <div className="space-y-1">
+                    {group.data.slice(0, 10).map((h: any, i: number) => {
+                      const val = Number(h[group.key] || 0);
+                      const barPct = Math.min(val, 100);
+                      const barColor = val > 85 ? 'bg-red-500' : val > 60 ? 'bg-amber-500' : 'bg-emerald-500';
+                      const dotColor = i < 3 ? (i === 0 ? 'text-red-400' : i === 1 ? 'text-amber-400' : 'text-orange-400') : 'text-slate-500';
+                      return (
+                        <div key={i} className="flex items-center gap-1.5 text-[11px]">
+                          <span className={`w-4 text-right font-mono font-bold ${dotColor}`}>
+                            {i === 0 ? '🥇' : i === 1 ? '🥈' : i === 2 ? '🥉' : `${i + 1}`}
+                          </span>
+                          <span className="w-24 truncate text-[var(--dg-text-secondary)]" title={h.hostname}>
+                            {h.hostname}
+                          </span>
+                          <div className="flex-1 h-1 rounded-full bg-[var(--dg-bg-tertiary)] overflow-hidden">
+                            <div className={`h-full rounded-full ${barColor}`} style={{ width: `${barPct}%` }} />
+                          </div>
+                          <span className="w-12 text-right font-mono text-[var(--dg-text-primary)]">{val.toFixed(1)}{group.unit}</span>
+                        </div>
+                      );
+                    })}
+                  </div>
+                </div>
+              ))}
+            </div>
+          )}
+        </CardContent>
+      </Card>
+
       {/* 顶部工具栏 */}
       <div className="flex items-center justify-between">
         <div className="flex items-center gap-4">