OIDC로 빠지는 분기 점검 login_challenge 복구 fallback 추가

userfront/lib/main.dart

@@ -147,14 +147,17 @@ final _router = GoRouter(
             GoRoute(
               path: 'login',
               builder: (context, state) {
+                final loginChallenge =
+                    state.uri.queryParameters['login_challenge'];
                 final redirectUrl =
                     state.uri.queryParameters['redirect_uri'] ??
                     state.uri.queryParameters['redirect_url'];
                 _routerLogger.info(
-                  "Navigating to /login, redirect: $redirectUrl",
+                  "Navigating to /login with login_challenge: $loginChallenge, redirect: $redirectUrl",
                 );
                 return LoginScreen(
                   key: state.pageKey,
+                  loginChallenge: loginChallenge,
                   redirectUrl: redirectUrl,
                 );
               },