feat: 重构 Dashboard 为卡片式分组布局

表格布局替换为按分组展示的卡片式布局，新增 group 字段配置和 TargetBoard/TargetCard 等组件。模态框详情页支持时间范围筛选和分页，SummaryCards 减为 3 个。API 端点变更：trend/history 改用 from/to 参数，history 支持分页。recentSampleCount 硬编码为 30。

src/web/hooks/useHistory.ts

@@ -0,0 +1,35 @@
+import { useCallback, useState } from "react";
+import type { HistoryResponse } from "../../shared/api";
+
+export function useHistory(targetId: number | null) {
+  const [data, setData] = useState<HistoryResponse>({ items: [], total: 0, page: 1, pageSize: 15 });
+  const [error, setError] = useState<string | null>(null);
+  const [loading, setLoading] = useState(false);
+
+  const fetchHistory = useCallback(
+    async (from: string, to: string, page = 1, pageSize = 15) => {
+      if (targetId === null) return;
+
+      setLoading(true);
+      setError(null);
+
+      try {
+        const response = await fetch(
+          `/api/targets/${targetId}/history?from=${encodeURIComponent(from)}&to=${encodeURIComponent(to)}&page=${page}&pageSize=${pageSize}`,
+        );
+
+        if (!response.ok) throw new Error(`HTTP ${response.status}`);
+
+        const result = (await response.json()) as HistoryResponse;
+        setData(result);
+      } catch (err) {
+        setError(err instanceof Error ? err.message : "请求失败");
+      } finally {
+        setLoading(false);
+      }
+    },
+    [targetId],
+  );
+
+  return { data, error, loading, fetchHistory };
+}