feat: i18n 개선 및 userfront 로그인/로케일 보완

userfront/lib/core/i18n/locale_utils.dart

@@ -0,0 +1,69 @@
+import 'dart:ui';
+
+import 'locale_storage.dart';
+
+const supportedLocaleCodes = ['en', 'ko'];
+const defaultLocaleCode = 'en';
+
+String normalizeLocaleCode(String? code) {
+  if (code == null || code.isEmpty) {
+    return defaultLocaleCode;
+  }
+  final normalized = code.toLowerCase();
+  if (normalized == 'ko' || normalized.startsWith('ko-')) {
+    return 'ko';
+  }
+  if (normalized == 'en' || normalized.startsWith('en-')) {
+    return 'en';
+  }
+  return defaultLocaleCode;
+}
+
+String resolvePreferredLocaleCode() {
+  final stored = LocaleStorage.read();
+  if (stored != null && supportedLocaleCodes.contains(stored)) {
+    return stored;
+  }
+  final deviceLocale = PlatformDispatcher.instance.locale;
+  return normalizeLocaleCode(deviceLocale.languageCode);
+}
+
+String? extractLocaleFromPath(Uri uri) {
+  if (uri.pathSegments.isEmpty) {
+    return null;
+  }
+  final code = uri.pathSegments.first.toLowerCase();
+  if (supportedLocaleCodes.contains(code)) {
+    return code;
+  }
+  return null;
+}
+
+String stripLocalePath(Uri uri) {
+  final segments = uri.pathSegments;
+  if (segments.isNotEmpty && supportedLocaleCodes.contains(segments.first)) {
+    final rest = segments.skip(1).join('/');
+    if (rest.isEmpty) {
+      return '/';
+    }
+    return '/$rest';
+  }
+  return uri.path;
+}
+
+String buildLocalizedPath(String localeCode, Uri uri) {
+  final segments = uri.pathSegments;
+  Iterable<String> restSegments = segments;
+  if (segments.isNotEmpty) {
+    final head = segments.first.toLowerCase();
+    if (supportedLocaleCodes.contains(head) || head.length == 2) {
+      restSegments = segments.skip(1);
+    }
+  }
+  final newSegments = [localeCode, ...restSegments];
+  final path = '/${newSegments.join('/')}';
+  if (uri.queryParameters.isEmpty) {
+    return path;
+  }
+  return Uri(path: path, queryParameters: uri.queryParameters).toString();
+}