refactor: 前端架构重构 — hook拆分、组件拆分、类型筛选器动态化、Meta API

- 后端新增 GET /api/meta 端点（checkerRegistry.supportedTypes）及 MetaResponse 类型
- 前端 hook 拆分为 use-queries.ts（全局查询+useMeta）和 use-target-detail.ts（Drawer状态）
- TargetDetailDrawer 拆分为 OverviewTab + HistoryTab + history-table-columns + stats.ts
- 类型筛选器由 meta API 动态驱动，删除 target-type-display 静态映射
- 列定义改为工厂函数 createTargetTableColumns(checkerTypes)，TargetGroup 新增 columns prop
- 修复 StatusDonut key、StatusBar maxSlots prop、TrendChart 移除 loading prop
- 补充 utils/time、utils/stats、动态列工厂测试，删除旧 mapping 测试
- 同步 delta specs 到主 specs，归档 frontend-architecture-refactor change

src/web/components/OverviewTab.tsx

@@ -0,0 +1,57 @@
+import { useMemo } from "react";
+import { Col, Descriptions, Divider, Row, Skeleton, Space, Statistic } from "tdesign-react";
+
+import type { TargetStatus, TrendPoint } from "../../shared/api";
+
+import { computeTrendStats } from "../utils/stats";
+import { StatusDonut } from "./StatusDonut";
+import { TrendChart } from "./TrendChart";
+
+interface OverviewTabProps {
+  target: TargetStatus;
+  trendData: TrendPoint[];
+  trendLoading: boolean;
+}
+
+export function OverviewTab({ target, trendData, trendLoading }: OverviewTabProps) {
+  const { downChecks, totalChecks, upChecks } = useMemo(() => computeTrendStats(trendData), [trendData]);
+
+  return (
+    <Space className="full-width" direction="vertical" size={16}>
+      <Divider align="left">统计</Divider>
+      <Row gutter={16}>
+        <Col span={3}>
+          <Statistic color="blue" title="总检查" value={totalChecks} />
+        </Col>
+        <Col span={3}>
+          <Statistic color="green" title="正常" value={upChecks} />
+        </Col>
+        <Col span={3}>
+          <Statistic color="red" title="异常" value={downChecks} />
+        </Col>
+        <Col span={3}>
+          <Statistic color="green" suffix="%" title="可用率" value={target.stats?.availability ?? 0} />
+        </Col>
+      </Row>
+
+      <Divider align="left">趋势</Divider>
+      {trendLoading ? <Skeleton animation="gradient" /> : <TrendChart data={trendData} />}
+
+      <Divider align="left">状态分布</Divider>
+      <StatusDonut down={downChecks} up={upChecks} />
+
+      <Divider align="left">基本信息</Divider>
+      <Descriptions
+        items={[
+          { content: target.target, label: "目标地址" },
+          { content: target.interval, label: "检查间隔" },
+          {
+            content: target.latestCheck ? new Date(target.latestCheck.timestamp).toLocaleString("zh-CN") : "-",
+            label: "最新检查时间",
+          },
+          { content: target.latestCheck?.statusDetail ?? "-", label: "状态详情" },
+        ]}
+      />
+    </Space>
+  );
+}