style: 优化前端样式，提升现代化设计感

- ConfigProvider 注入全局配置（动画、表格尺寸）
- CSS Variables 主题微调（页面背景、圆角、字体栈）
- AppLayout Menu 支持 logo/operations/collapsed
- Statistic 组件增加 color/prefix/suffix/animation
- Card 组件启用 hoverShadow/headerBordered
- Table 组件启用 stripe 斑马纹
- Tag 组件使用 variant="light" + shape="round"
- Dialog 居中显示并设置固定宽度
- 布局样式硬编码颜色替换为 TDesign Token
- UsageChart 改用 AreaChart + 渐变填充
- 更新 frontend spec 同步样式体系要求

frontend/src/components/AppLayout/index.tsx

@@ -1,5 +1,6 @@
-import { Layout, Menu } from 'tdesign-react';
-import { ServerIcon, ChartLineIcon, SettingIcon } from 'tdesign-icons-react';
+import { useState } from 'react';
+import { Layout, Menu, Button } from 'tdesign-react';
+import { ServerIcon, ChartLineIcon, SettingIcon, ChevronLeftIcon, ChevronRightIcon } from 'tdesign-icons-react';
 import { Outlet, useLocation, useNavigate } from 'react-router';
 
 const { MenuItem } = Menu;
@@ -7,6 +8,7 @@ const { MenuItem } = Menu;
 export function AppLayout() {
   const location = useLocation();
   const navigate = useNavigate();
+  const [collapsed, setCollapsed] = useState(false);
 
   const getPageTitle = () => {
     if (location.pathname === '/providers') return '供应商管理';
@@ -15,10 +17,12 @@ export function AppLayout() {
     return 'AI Gateway';
   };
 
+  const asideWidth = collapsed ? '64px' : '232px';
+
   return (
     <Layout style={{ minHeight: '100vh' }}>
       <Layout.Aside
-        width="232px"
+        width={asideWidth}
         style={{
           overflow: 'hidden',
           height: '100vh',
@@ -28,45 +32,52 @@ export function AppLayout() {
           bottom: 0,
         }}
       >
-        <div style={{ display: 'flex', flexDirection: 'column', height: '100%' }}>
-          <div
-            style={{
+        <Menu
+          value={location.pathname}
+          onChange={(value) => navigate(value as string)}
+          collapsed={collapsed}
+          width={['232px', '64px']}
+          logo={
+            <div style={{
               height: 64,
               display: 'flex',
               alignItems: 'center',
               justifyContent: 'center',
               fontSize: '1.25rem',
               fontWeight: 600,
-              flexShrink: 0,
-            }}
-          >
-            AI Gateway
-          </div>
-          <Menu
-            value={location.pathname}
-            onChange={(value) => navigate(value as string)}
-            style={{ flex: 1, overflow: 'auto' }}
-          >
-            <MenuItem value="/providers" icon={<ServerIcon />}>
-              供应商管理
-            </MenuItem>
-            <MenuItem value="/stats" icon={<ChartLineIcon />}>
-              用量统计
-            </MenuItem>
-            <MenuItem value="/settings" icon={<SettingIcon />}>
-              设置
-            </MenuItem>
-          </Menu>
-        </div>
+            }}>
+              {!collapsed && 'AI Gateway'}
+            </div>
+          }
+          operations={
+            <Button
+              variant="text"
+              shape="square"
+              icon={collapsed ? <ChevronRightIcon /> : <ChevronLeftIcon />}
+              onClick={() => setCollapsed(!collapsed)}
+            />
+          }
+          style={{ height: '100%' }}
+        >
+          <MenuItem value="/providers" icon={<ServerIcon />}>
+            供应商管理
+          </MenuItem>
+          <MenuItem value="/stats" icon={<ChartLineIcon />}>
+            用量统计
+          </MenuItem>
+          <MenuItem value="/settings" icon={<SettingIcon />}>
+            设置
+          </MenuItem>
+        </Menu>
       </Layout.Aside>
-      <Layout style={{ marginLeft: 232 }}>
+      <Layout style={{ marginLeft: asideWidth }}>
         <Layout.Header
           style={{
             padding: '0 2rem',
-            background: '#fff',
+            background: 'var(--td-bg-color-container)',
             display: 'flex',
             alignItems: 'center',
-            borderBottom: '1px solid #e7e7e7',
+            borderBottom: '1px solid var(--td-component-stroke)',
           }}
         >
           <h1 style={{ margin: 0, fontSize: '1.25rem' }}>{getPageTitle()}</h1>