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 }}>

frontend/src/pages/About/index.tsx

@@ -0,0 +1,30 @@
+import { Card } from 'tdesign-react'
+
+export default function AboutPage() {
+  return (
+    <Card bordered={false}>
+      <div
+        style={{
+          display: 'flex',
+          flexDirection: 'column',
+          alignItems: 'center',
+          justifyContent: 'center',
+          padding: '4rem 0',
+        }}
+      >
+        <h1 style={{ margin: 0, fontSize: '2rem' }}>Nex</h1>
+        <p style={{ margin: '0.5rem 0 0', color: 'var(--td-text-color-secondary)', fontSize: '1rem' }}>
+          AI Gateway - 统一的大模型 API 网关
+        </p>
+        <a
+          href='https://github.com/nex/gateway'
+          target='_blank'
+          rel='noopener noreferrer'
+          style={{ marginTop: '1rem', color: 'var(--td-brand-color)' }}
+        >
+          https://github.com/nex/gateway
+        </a>
+      </div>
+    </Card>
+  )
+}

frontend/src/routes/index.tsx

@@ -6,6 +6,7 @@ import { AppLayout } from '@/components/AppLayout'
 const ProvidersPage = lazy(() => import('@/pages/Providers'))
 const StatsPage = lazy(() => import('@/pages/Stats'))
 const SettingsPage = lazy(() => import('@/pages/Settings'))
+const AboutPage = lazy(() => import('@/pages/About'))
 const NotFound = lazy(() => import('@/pages/NotFound'))
 
 export function AppRoutes() {
@@ -17,6 +18,7 @@ export function AppRoutes() {
           <Route path='providers' element={<ProvidersPage />} />
           <Route path='stats' element={<StatsPage />} />
           <Route path='settings' element={<SettingsPage />} />
+          <Route path='about' element={<AboutPage />} />
           <Route path='*' element={<NotFound />} />
         </Route>
       </Routes>