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/useTrend.ts

@@ -6,25 +6,30 @@ export function useTrend(targetId: number | null) {
   const [error, setError] = useState<string | null>(null);
   const [loading, setLoading] = useState(false);
 
-  const fetchTrend = useCallback(async () => {
-    if (targetId === null) return;
+  const fetchTrend = useCallback(
+    async (from: string, to: string) => {
+      if (targetId === null) return;
 
-    setLoading(true);
-    setError(null);
+      setLoading(true);
+      setError(null);
 
-    try {
-      const response = await fetch(`/api/targets/${targetId}/trend?hours=24`);
+      try {
+        const response = await fetch(
+          `/api/targets/${targetId}/trend?from=${encodeURIComponent(from)}&to=${encodeURIComponent(to)}`,
+        );
 
-      if (!response.ok) throw new Error(`HTTP ${response.status}`);
+        if (!response.ok) throw new Error(`HTTP ${response.status}`);
 
-      const result = (await response.json()) as TrendPoint[];
-      setData(result);
-    } catch (err) {
-      setError(err instanceof Error ? err.message : "请求失败");
-    } finally {
-      setLoading(false);
-    }
-  }, [targetId]);
+        const result = (await response.json()) as TrendPoint[];
+        setData(result);
+      } catch (err) {
+        setError(err instanceof Error ? err.message : "请求失败");
+      } finally {
+        setLoading(false);
+      }
+    },
+    [targetId],
+  );
 
   return { data, error, loading, fetchTrend };
 }