fix(dashboard): 资源趋势图移除随机模拟数据

- 无主机/无指标时不再用 Math.random 生成假曲线，改为空状态提示
- 移除随之不再使用的 avgCpu/avgMemory props，新增中英文 noData 文案

frontend/src/components/dashboard/Dashboard.tsx

@@ -148,8 +148,6 @@ export function Dashboard() {
       {/* 资源使用率趋势 — 第一行 */}
       <div className="animate-fade-in-delay-1">
         <ResourceUsageCard
-          avgCpu={Number(serverStats?.avg_cpu ?? 0)}
-          avgMemory={Number(serverStats?.avg_memory ?? 0)}
           avgDisk={Number(serverStats?.avg_disk ?? 0)}
           totalCpu={Number(serverStats?.total_cpu ?? 0)}
           totalMemory={Number(serverStats?.total_memory ?? 0)}

frontend/src/components/dashboard/DashboardCharts.tsx

@@ -56,19 +56,7 @@ export function computeMonthChange( monthTrend: JsonData[]): {
   return { pct, label, direction };
 }
 
-function generateMetricsData(avgCpu: number, avgMemory: number, avgDisk: number, points = 24) {
-  const data = [];
-  for (let i = points - 1; i >= 0; i--) {
-    const d = new Date(Date.now() - i * 60 * 60 * 1000);
-    data.push({
-      time: `${d.getHours().toString().padStart(2, '0')}:00`,
-      cpu: Number(Math.max(0, Math.min(100, avgCpu + (Math.random() - 0.5) * 15)).toFixed(1)),
-      memory: Number(Math.max(0, Math.min(100, avgMemory + (Math.random() - 0.5) * 10)).toFixed(1)),
-      disk: Number(Math.max(0, Math.min(100, avgDisk + (Math.random() - 0.5) * 5)).toFixed(1)),
-    });
-  }
-  return data;
-}
+// 无真实指标时不再生成模拟曲线，避免“没有主机却有波动”的误导展示 // Logan.Li
 
 function buildMetricsFromReal( metrics: JsonData[], avgDisk: number) {
   if (!metrics || metrics.length === 0) return [];
@@ -291,8 +279,6 @@ export function TopResourceUsageCard({ topUsage }: { topUsage: JsonData}) {
 }
 
 export function ResourceUsageCard({
-  avgCpu,
-  avgMemory,
   avgDisk,
   totalCpu,
   totalMemory,
@@ -301,8 +287,6 @@ export function ResourceUsageCard({
   usedDisk,
   metrics,
 }: {
-  avgCpu: number;
-  avgMemory: number;
   avgDisk: number;
   totalCpu: number;
   totalMemory: number;
@@ -312,7 +296,6 @@ export function ResourceUsageCard({
   metrics?: JsonData[];
 }) {
   const realData = buildMetricsFromReal(metrics ?? [], avgDisk);
-  const data = realData.length > 0 ? realData : generateMetricsData(avgCpu, avgMemory, avgDisk, 24);
   const { t } = useTranslation();
 
   return (
@@ -358,6 +341,7 @@ export function ResourceUsageCard({
         </div>
       </CardHeader>
       <CardContent>
+        {realData.length > 0 ? (
         <div className="h-[280px]">
           <ResponsiveContainer width="100%" height="100%">
             <AreaChart data={data} margin={{ top: 10, right: 10, left: 0, bottom: 0 }}>
@@ -385,6 +369,13 @@ export function ResourceUsageCard({
             </AreaChart>
           </ResponsiveContainer>
         </div>
+        ) : (
+          /* 空状态：无主机/无指标时明确提示，不再展示模拟波动 // Logan.Li */
+          <div className="h-[280px] flex flex-col items-center justify-center gap-2 text-[var(--dg-text-muted)]">
+            <Activity className="h-8 w-8 opacity-40" />
+            <p className="text-sm">{t('dashboard.resourceUsage.noData')}</p>
+          </div>
+        )}
       </CardContent>
     </Card>
   );