OIDC로 빠지는 분기 점검 login_challenge 복구 fallback 추가

userfront/lib/core/services/web_window_stub.dart

@@ -3,6 +3,14 @@ class WebWindow {
 
   void redirectTo(String url) {}
 
+  String currentHref() {
+    return '';
+  }
+
+  String currentSearch() {
+    return '';
+  }
+
   void alert(String message) {}
 
   void close() {}

userfront/lib/core/services/web_window_web.dart

@@ -1,6 +1,7 @@
 // ignore_for_file: avoid_web_libraries_in_flutter, deprecated_member_use
 
 import 'dart:html' as html;
+import 'package:flutter/foundation.dart';
 
 class WebWindow {
   void setTitle(String title) {
@@ -8,7 +9,48 @@ class WebWindow {
   }
 
   void redirectTo(String url) {
+    final currentHref = html.window.location.href;
+    Uri? targetUri;
+    try {
+      targetUri = Uri.parse(url);
+    } catch (_) {
+      debugPrint("[WebWindow] redirectTo parse failed: url=$url");
+    }
+
+    final currentPort = int.tryParse(html.window.location.port);
+    final sameOrigin =
+        targetUri != null &&
+        targetUri.scheme == html.window.location.protocol.replaceAll(':', '') &&
+        targetUri.host == html.window.location.hostname &&
+        (!targetUri.hasPort || targetUri.port == currentPort);
+
+    debugPrint(
+      "[WebWindow] redirectTo start: current=$currentHref, target=$url, target_host=${targetUri?.host ?? ''}, target_path=${targetUri?.path ?? ''}, same_origin=$sameOrigin",
+    );
+
     html.window.location.href = url;
+
+    // 이동이 차단되거나 즉시 원위치되는 경우를 추적하기 위한 후속 로그입니다.
+    Future<void>.delayed(const Duration(milliseconds: 800), () {
+      final nowHref = html.window.location.href;
+      if (nowHref == currentHref) {
+        debugPrint(
+          "[WebWindow] redirectTo no-op detected: current URL did not change after navigation attempt",
+        );
+      } else {
+        debugPrint(
+          "[WebWindow] redirectTo post-check: location changed to $nowHref",
+        );
+      }
+    });
+  }
+
+  String currentHref() {
+    return html.window.location.href;
+  }
+
+  String currentSearch() {
+    return html.window.location.search ?? '';
   }
 
   void alert(String message) {