fix: NotificationPage 添加渠道弹框 X 图标未 import 导致报错

frontend/src/pages/NotificationPage.tsx

@@ -1,6 +1,6 @@
 import { useState, useEffect, useCallback } from 'react';
 import request from '@/api/request';
-import { Plus, Trash2, Send, Bell, Mail, Settings } from 'lucide-react';
+import { Plus, Trash2, Send, Bell, Mail, Settings, X } from 'lucide-react';
 import { ConfirmDialog } from '@/components/ConfirmDialog';
 import { FormDialog } from '@/components/FormDialog';
 import { ModalOverlay } from '@/components/ModalOverlay';