refactor(web): 前端改用 @stash/ui 组件库

- 新增本地依赖 @stash/ui（file:../../stash-ui），引入其 style.css 与设计令牌
- 页面骨架改用 Layout（contained + header/sider），搜索框改为吸顶
- 卡片/菜单/按钮/标签/头像/分页/空态/提示全部换成组件库组件
- 删除本地 iconfont 与 1400 行手写组件样式，App.css 只保留页面级样式
- 数据层、路由、过滤逻辑未改动；33 个 Rust 测试通过

stash-web/src/components/content/DetailView.tsx

@@ -1,3 +1,4 @@
+import { Badge, Breadcrumb, Button, Card, Empty, Space, Title } from '@stash/ui'
 import { categoryCount, type Category } from '../../data/types'
 import { AppGrid } from './AppGrid'
 import { CesCardGrid } from './CesCardGrid'
@@ -28,10 +29,14 @@ export function DetailView({ category, groupId, onBack, onOpenItem }: DetailView
 
   const title = activeGroup?.name ?? category.title
   const count = activeGroup !== undefined ? activeGroup.items.length : categoryCount(category)
-  const breadcrumb =
+  const crumbs =
     activeGroup !== undefined
-      ? `首页 / ${category.title} / ${activeGroup.name}`
-      : `首页 / ${category.title}`
+      ? [
+          { label: '首页', href: '/' },
+          { label: category.title },
+          { label: activeGroup.name },
+        ]
+      : [{ label: '首页', href: '/' }, { label: category.title }]
 
   function renderBody() {
     if (category.kind === 'posters') {
@@ -51,33 +56,35 @@ export function DetailView({ category, groupId, onBack, onOpenItem }: DetailView
     }
 
     if (category.groups.length === 0) {
-      return <p className="section-empty">{category.emptyText ?? '暂无内容'}</p>
+      return <Empty text={category.emptyText ?? '暂无内容'} />
     }
 
     return (
-      <>
+      <Space direction="column" gap="lg" align="stretch">
         {category.groups.map((group) => (
           <GroupBlock key={group.id} group={group} onOpen={onOpenItem} />
         ))}
-      </>
+      </Space>
     )
   }
 
   return (
     <div className="detail-view">
-      <div className="detail-nav card-box">
-        <button type="button" className="detail-back" onClick={onBack}>
-          返回首页
-        </button>
-        <span className="detail-breadcrumb">{breadcrumb}</span>
-      </div>
+      <Card padding="sm">
+        <Space justify="between" wrap>
+          <Button variant="ghost" size="sm" onClick={onBack}>
+            返回首页
+          </Button>
+          <Breadcrumb items={crumbs} />
+        </Space>
+      </Card>
 
       <div className="detail-hero">
         <span className="detail-hero-icon" aria-hidden="true">
           {category.icon}
         </span>
-        <h2 className="detail-hero-title">{title}</h2>
-        <span className="detail-hero-count">[{count}]</span>
+        <Title level={2}>{title}</Title>
+        <Badge count={count} tone="neutral" />
       </div>
 
       {renderBody()}