로그인 화면 아이디/비밀번호 입력칸 폭 제한 (데스크톱 웹에서 너무 넓게 늘어지던 문제 수정)

lib/screens/login_screen.dart

@@ -421,6 +421,8 @@ class _LoginScreenState extends State<LoginScreen> {
       body: Center(
         child: SingleChildScrollView(
           padding: const EdgeInsets.all(24.0),
+          child: ConstrainedBox(
+            constraints: const BoxConstraints(maxWidth: 420),
             child: Column(
               mainAxisAlignment: MainAxisAlignment.center,
               children: [
@@ -506,7 +508,11 @@ class _LoginScreenState extends State<LoginScreen> {
                   mainAxisAlignment: MainAxisAlignment.spaceEvenly,
                   children: [
                     TextButton.icon(
-                    icon: const Icon(Icons.gavel, size: 18, color: Colors.grey),
+                      icon: const Icon(
+                        Icons.gavel,
+                        size: 18,
+                        color: Colors.grey,
+                      ),
                       label: const Text(
                         '교사 간편인증',
                         style: TextStyle(color: Colors.grey),
@@ -539,6 +545,7 @@ class _LoginScreenState extends State<LoginScreen> {
             ),
           ),
         ),
+      ),
     );
   }
 }