fix: 仪表盘资源趋势图使用真实Agent指标替代随机假数据

- 后端 GetMetrics 修复 strftime 字符串无法扫入 time.Time 导致 timestamp 为零值的 bug
  (改为 string 类型 + time.ParseInLocation 手动解析)
- 前端 Dashboard.tsx 新增 getMetrics(24) 调用，获取真实按小时聚合的 Agent 数据
- DashboardCharts.tsx 新增 buildMetricsFromReal() 将 MetricData[] 转换为图表数据
- ResourceUsageCard 优先使用真实时间序列，无数据时回退到平均值生成

frontend/src/components/dashboard/Dashboard.tsx

@@ -20,12 +20,13 @@ export function Dashboard() {
   const [alerts, setAlerts] = useState<any[]>([]);
   const [releases, setReleases] = useState<any[]>([]);
   const [expCerts, setExpCerts] = useState<any[]>([]);
+  const [metrics, setMetrics] = useState<any[]>([]); // 真实 Agent 指标时间序列 // Logan.Li
 
   useEffect(() => {
     const fetchData = async () => {
       setLoading(true);
       try {
-        const [statsRes, serversRes, clustersRes, alertsRes, releasesRes] = await Promise.all([
+        const [statsRes, serversRes, clustersRes, alertsRes, releasesRes, metricsRes] = await Promise.all([
           dashboardStatsApi.getStats().catch((e) => {
             console.error('Failed to fetch dashboard stats:', e);
             return null;
@@ -46,6 +47,11 @@ export function Dashboard() {
             console.error('Failed to fetch dashboard releases:', e);
             return null;
           }),
+          // 获取真实 Agent 指标时间序列（过去24小时按小时聚合） // Logan.Li
+          dashboardStatsApi.getMetrics(24).catch((e) => {
+            console.error('Failed to fetch metrics:', e);
+            return [];
+          }),
         ]);
 
         setStats(statsRes);
@@ -54,6 +60,7 @@ export function Dashboard() {
         setAlerts(Array.isArray(alertsRes) ? alertsRes : []);
         setReleases(Array.isArray(releasesRes) ? releasesRes : []);
         setExpCerts(statsRes?.expiring_certs ?? []);
+        setMetrics(Array.isArray(metricsRes) ? metricsRes : []);
       } catch (error) {
         console.error('Failed to load dashboard data:', error);
       } finally {
@@ -142,6 +149,7 @@ export function Dashboard() {
         avgCpu={Number(serverStats?.avg_cpu ?? 0)}
         avgMemory={Number(serverStats?.avg_memory ?? 0)}
         avgDisk={Number(serverStats?.avg_disk ?? 0)}
+        metrics={metrics}
       />
 
       {/* Cost & Top Resource Usage */}

frontend/src/components/dashboard/DashboardCharts.tsx

@@ -248,17 +248,46 @@ export function TopResourceUsageCard({ topUsage }: { topUsage: any }) {
   );
 }
 
+// 将后端 MetricData[] 时间序列转换为图表所需格式 { time, cpu, memory } // Logan.Li
+function buildMetricsFromReal(metrics: any[], avgDisk: number): { time: string; cpu: number; memory: number; disk: number }[] {
+  if (!metrics || metrics.length === 0) return [];
+  // 按 timestamp 分组：同一时刻有 cpu + memory 两条记录
+  const buckets: Record<string, { cpu?: number; memory?: number }> = {};
+  for (const m of metrics) {
+    const ts = m.timestamp;
+    if (!ts) continue;
+    // 提取 HH:MM 格式作为 X 轴标签
+    const d = new Date(ts);
+    const label = `${d.getHours().toString().padStart(2, '0')}:00`;
+    if (!buckets[label]) buckets[label] = {};
+    if (m.name === 'cpu') buckets[label].cpu = Number(m.value) || 0;
+    if (m.name === 'memory') buckets[label].memory = Number(m.value) || 0;
+  }
+  return Object.entries(buckets)
+    .sort((a, b) => a[0].localeCompare(b[0]))
+    .map(([time, v]) => ({
+      time,
+      cpu: Number((v.cpu ?? 0).toFixed(1)),
+      memory: Number((v.memory ?? 0).toFixed(1)),
+      disk: Number(avgDisk.toFixed(1)), // 磁盘无历史序列，用平均值
+    }));
+}
+
 // 资源使用率趋势卡片
 export function ResourceUsageCard({
   avgCpu,
   avgMemory,
   avgDisk,
+  metrics,
 }: {
   avgCpu: number;
   avgMemory: number;
   avgDisk: number;
+  metrics?: any[];
 }) {
-  const data = generateMetricsData(avgCpu, avgMemory, avgDisk, 24);
+  // 优先使用真实 Agent 指标时间序列；无数据时回退到平均值生成（带随机波动） // Logan.Li
+  const realData = buildMetricsFromReal(metrics ?? [], avgDisk);
+  const data = realData.length > 0 ? realData : generateMetricsData(avgCpu, avgMemory, avgDisk, 24);
 
   return (
     <Card className="bg-slate-900 border-slate-800">