perf: 并行化 admin 聚合路由并完善前端缓存预取

- gateway: usage detail / provider summary / pool overview / users list 改为 tokio join 并行拉取依赖数据
- usage: interval timeline 支持自动刷新并按查询区间动态展示，取消服务端 120 分钟过滤并在 ScatterChart 统一封顶
- frontend: 新增管理端导航预取工具及 SidebarNav/MainLayout 触发，admin 读接口统一走 cachedRequest 的短期缓存
- dashboard: request detail 支持短 TTL 缓存并在 UsageRecordsTable mousedown 时预取
- data: migrate 测试在 wait_for_postgres 失败时清理子进程，避免遗留

frontend/src/components/charts/ScatterChart.vue

@@ -290,10 +290,10 @@ function transformData(data: ChartData<'scatter'>): ChartData<'scatter'> {
     ...data,
     datasets: data.datasets.map(dataset => ({
       ...dataset,
-      data: (dataset.data as Array<{ x: string; y: number; _originalX?: string }>).map(point => ({
+      data: (dataset.data as Array<{ x: string; y: number; _originalX?: string; _originalY?: number }>).map(point => ({
         ...point,
-        y: toDisplayValue(point.y),
-        _originalY: point.y  // 保存原始值用于 tooltip
+        y: toDisplayValue(Math.min(point.y, 120)),
+        _originalY: point._originalY ?? point.y  // 保存原始值用于 tooltip
       }))
     }))
   }

frontend/src/components/layout/SidebarNav.vue

@@ -29,6 +29,9 @@
                 ? 'bg-primary/10 text-primary font-medium'
                 : 'text-muted-foreground hover:text-foreground hover:bg-muted/50'
             ]"
+            @mouseenter="emit('prefetch', item.href)"
+            @focus="emit('prefetch', item.href)"
+            @pointerdown="emit('prefetch', item.href)"
             @click="handleNavigate(item.href)"
           >
             <div class="flex items-center gap-2.5">
@@ -76,6 +79,7 @@ const props = defineProps<{
 
 const emit = defineEmits<{
   (e: 'navigate', href: string): void
+  (e: 'prefetch', href: string): void
 }>()
 
 function isItemActive(href: string) {