feat: 将"关于"从系统托盘原生对话框迁移到前端页面

移除系统托盘右键菜单中的"关于"选项及各平台原生对话框实现，
在前端新增 /about 路由和关于页面展示品牌信息，侧边栏增加关于导航入口

frontend/src/components/AppLayout/index.tsx

@@ -1,6 +1,13 @@
 import { useState } from 'react'
 import { Outlet, useLocation, useNavigate } from 'react-router'
-import { ServerIcon, ChartLineIcon, SettingIcon, ChevronLeftIcon, ChevronRightIcon } from 'tdesign-icons-react'
+import {
+  ServerIcon,
+  ChartLineIcon,
+  SettingIcon,
+  InfoCircleIcon,
+  ChevronLeftIcon,
+  ChevronRightIcon,
+} from 'tdesign-icons-react'
 import { Layout, Menu, Button } from 'tdesign-react'
 
 const { MenuItem } = Menu
@@ -14,6 +21,7 @@ export function AppLayout() {
     if (location.pathname === '/providers') return '供应商管理'
     if (location.pathname === '/stats') return '用量统计'
     if (location.pathname === '/settings') return '设置'
+    if (location.pathname === '/about') return '关于'
     return 'AI Gateway'
   }
 
@@ -70,6 +78,9 @@ export function AppLayout() {
           <MenuItem value='/settings' icon={<SettingIcon />}>
             设置
           </MenuItem>
+          <MenuItem value='/about' icon={<InfoCircleIcon />}>
+            关于
+          </MenuItem>
         </Menu>
       </Layout.Aside>
       <Layout style={{ marginLeft: asideWidth }}>