fix login

frontend/src/components/auth/LoginCallback.tsx

@@ -1,4 +1,4 @@
-import React, { useEffect, useState } from 'react';
+import React, { useEffect, useRef, useState } from 'react';
 import { useNavigate, useSearchParams } from 'react-router-dom';
 import { useAuth } from '../../contexts/AuthContext';
 import { Box, CircularProgress, Typography, Alert, Button } from '@mui/material';
@@ -8,8 +8,12 @@ const LoginCallback: React.FC = () => {
   const [searchParams] = useSearchParams();
   const { login } = useAuth();
   const [error, setError] = useState<string>('');
+  const hasCalledLogin = useRef(false);
 
   useEffect(() => {
+    if (hasCalledLogin.current) return;
+    hasCalledLogin.current = true;
+
     const handleCallback = async () => {
       const code = searchParams.get('code');
       const errorParam = searchParams.get('error');