fix: replace lucide-react Sparkles with RobotOutlined to avoid extra dependency

apps/admin/src/layouts/MainLayout.tsx

@@ -1,6 +1,5 @@
 import React, { useCallback, useEffect, useMemo, useRef, useState } from 'react';
 import { Outlet, useNavigate, useLocation } from 'react-router-dom';
-import { Sparkles } from 'lucide-react';
 import { Layout, Menu, Button, Avatar, Dropdown, Drawer, Grid, Tooltip } from 'antd';
 import {
   DashboardOutlined,
@@ -274,7 +273,7 @@ const MainLayout: React.FC = () => {
                 <Button
                   type="text"
                   aria-label="打开 AI 助理"
-                  icon={<Sparkles size={17} strokeWidth={1.8} />}
+                  icon={<RobotOutlined style={{ fontSize: 17 }} />}
                   onClick={() => setAiChatOpen(true)}
                 />
               </Tooltip>