fix(findings): 「按资产」视图资产列表溢出时补回滚动条

左侧资产树的滚动容器靠 height:100% 取高，但外层卡片只给了 max-height
没有确定高度，百分比高度解析失败，资产多时列表撑破卡片或被截断且无法
滚动。改为把高度上限直接放到资产树的原生滚动容器上（overflow-y-auto +
max-h，随窗口自适应），资产少随内容收缩、资产多封顶并出滚动条。

Closes #170

web/src/app/(main)/function/findings/_components/asset-tree.tsx

@@ -18,7 +18,6 @@ import {
 
 import { Button } from "@/components/ui/button";
 import { InputGroup, InputGroupAddon, InputGroupInput } from "@/components/ui/input-group";
-import { ScrollArea } from "@/components/ui/scroll-area";
 import type { FindingAssetKind, FindingAssetNode } from "@/lib/types";
 import { cn } from "@/lib/utils";
 
@@ -299,12 +298,12 @@ export function AssetTree({
         <span className="text-xs tabular-nums text-muted-foreground">{findingTotal}</span>
       </button>
 
-      <ScrollArea className="min-h-0 flex-1">
-        <div className="flex flex-col pr-2">
+      <div className="max-h-[24rem] min-h-0 flex-1 overflow-y-auto pr-2 lg:max-h-[calc(100vh-16rem)]">
+        <div className="flex flex-col">
           {rows}
           {rows.length === 0 && <p className="px-2 py-8 text-center text-xs text-muted-foreground">{emptyHint}</p>}
         </div>
-      </ScrollArea>
+      </div>
 
       {truncated && (
         <p className="px-1 text-xs text-muted-foreground">

web/src/app/(main)/function/findings/page.tsx

@@ -964,7 +964,7 @@ export default function FindingsPage() {
         {view === "asset" && (
           <div className="grid min-h-0 items-start gap-4 lg:grid-cols-[20rem_minmax(0,1fr)] xl:grid-cols-[24rem_minmax(0,1fr)]">
             <Card className="gap-0 py-3 lg:sticky lg:top-4">
-              <CardContent className="flex max-h-[24rem] flex-col px-3 lg:max-h-[calc(100vh-14rem)]">
+              <CardContent className="flex flex-col px-3">
                 {assetTree.loading && !assetTree.loaded ? (
                   <div className="flex min-h-36 items-center justify-center">
                     <Spinner />