feat: 前端指标体系增强 — Dashboard/Metrics API、2×4 统计区、趋势图面积+异常标记、连续状态列

- 新增 GET /api/dashboard 合并原 summary+targets 首屏接口
- 新增 GET /api/targets/:id/metrics 合并原 stats+trend 概览接口
- 后端指标纯函数：可用率、百分位、故障段分析、连续状态、UTC 小时分桶
- ProbeStore 窗口取数方法替代全量历史查询
- SummaryCards 扩展为 4 卡片（新增异常事件数）+ 数据新鲜度展示
- 表格新增「连续」列（Tag 渲染 capped 状态）
- OverviewTab 重构为 2×4 Statistic 多维度布局
- TrendChart 改为延迟范围面积图 + 红色异常标记点
- 删除旧路由（summary/targets/trend）和 computeTrendStats
- 同步 delta specs 到主 specs 并归档变更

src/web/hooks/use-target-detail.ts

@@ -1,14 +1,13 @@
 import { useQuery, useQueryClient } from "@tanstack/react-query";
 import { useCallback, useState } from "react";
 
-import type { HistoryResponse, TargetStatus, TrendPoint } from "../../shared/api";
+import type { HistoryResponse, TargetStatus } from "../../shared/api";
 
 import { subtractHours } from "../utils/time";
-import { fetchJson, useTargets } from "./use-queries";
+import { fetchJson, useDashboard, useTargetMetrics } from "./use-queries";
 
 const detailQueryKeys = {
   history: (targetId: number, from: string, to: string, page: number) => ["history", targetId, from, to, page] as const,
-  trend: (targetId: number, from: string, to: string) => ["trend", targetId, from, to] as const,
 };
 
 export function useTargetDetail() {
@@ -18,28 +17,22 @@ export function useTargetDetail() {
   const [timeTo, setTimeTo] = useState("");
   const [historyPage, setHistoryPage] = useState(1);
 
-  const { data: targetsData } = useTargets();
+  const { data: dashboardData } = useDashboard();
   const selectedTarget =
-    selectedTargetId !== null ? (targetsData?.find((target) => target.id === selectedTargetId) ?? null) : null;
+    selectedTargetId !== null
+      ? (dashboardData?.targets.find((target) => target.id === selectedTargetId) ?? null)
+      : null;
 
-  const trend = useQuery({
-    enabled: selectedTargetId !== null && !!timeFrom && !!timeTo,
-    queryFn: () =>
-      fetchJson<TrendPoint[]>(
-        `/api/targets/${selectedTargetId}/trend?from=${encodeURIComponent(timeFrom)}&to=${encodeURIComponent(timeTo)}`,
-      ),
-    queryKey:
-      selectedTargetId !== null && timeFrom && timeTo
-        ? detailQueryKeys.trend(selectedTargetId, timeFrom, timeTo)
-        : ["trend", "disabled"],
-  });
+  const metrics = useTargetMetrics(selectedTargetId, timeFrom, timeTo, "1h");
 
   const history = useQuery({
     enabled: selectedTargetId !== null && !!timeFrom && !!timeTo,
-    queryFn: () =>
-      fetchJson<HistoryResponse>(
+    queryFn: () => {
+      if (selectedTargetId === null) throw new Error("未选择目标");
+      return fetchJson<HistoryResponse>(
         `/api/targets/${selectedTargetId}/history?from=${encodeURIComponent(timeFrom)}&to=${encodeURIComponent(timeTo)}&page=${historyPage}&pageSize=20`,
-      ),
+      );
+    },
     queryKey:
       selectedTargetId !== null && timeFrom && timeTo
         ? detailQueryKeys.history(selectedTargetId, timeFrom, timeTo, historyPage)
@@ -57,7 +50,7 @@ export function useTargetDetail() {
 
   const closeDrawer = useCallback(() => {
     setSelectedTargetId(null);
-    queryClient.removeQueries({ queryKey: ["trend"] });
+    queryClient.removeQueries({ queryKey: ["metrics"] });
     queryClient.removeQueries({ queryKey: ["history"] });
   }, [queryClient]);
 
@@ -77,11 +70,11 @@ export function useTargetDetail() {
     handleTimeChange,
     historyData: history.data ?? { items: [], page: 1, pageSize: 20, total: 0 },
     historyLoading: history.isLoading,
+    metricsData: metrics.data ?? null,
+    metricsLoading: metrics.isLoading,
     openDrawer,
     selectedTarget,
     timeFrom,
     timeTo,
-    trendData: trend.data ?? [],
-    trendLoading: trend.isLoading,
   };
 }