ci: enforce flutter/biome format checks and fix front lint violations

userfront/lib/core/i18n/locale_gate.dart

@@ -34,16 +34,12 @@ class _LocaleGateState extends State<LocaleGate> {
   Future<void> _applyLocale() async {
     final normalized = normalizeLocaleCode(widget.localeCode);
     LocaleStorage.write(normalized);
-    webWindow.setTitle(
-      tr('ui.userfront.app_title'),
-    );
+    webWindow.setTitle(tr('ui.userfront.app_title'));
     if (context.locale.languageCode == normalized) {
       return;
     }
     await context.setLocale(Locale(normalized));
-    webWindow.setTitle(
-      tr('ui.userfront.app_title'),
-    );
+    webWindow.setTitle(tr('ui.userfront.app_title'));
   }
 
   @override

userfront/lib/core/i18n/locale_utils.dart

@@ -76,7 +76,7 @@ String buildLocalizedPath(String localeCode, Uri uri) {
     }
   }
   final newPath = '/${[localeCode, ...restSegments].join('/')}';
-  
+
   // Return only the path and query part to avoid GoRouter confusion with full URLs
   final newUri = uri.replace(path: newPath);
   String result = newUri.path;

userfront/lib/core/services/auth_proxy_service.dart

@@ -299,10 +299,7 @@ class AuthProxyService {
       } else {
         final errorBody = jsonDecode(response.body);
         throw Exception(
-          errorBody['error'] ??
-              tr(
-                'err.userfront.auth_proxy.consent_fetch',
-              ),
+          errorBody['error'] ?? tr('err.userfront.auth_proxy.consent_fetch'),
         );
       }
     } finally {
@@ -333,10 +330,7 @@ class AuthProxyService {
       } else {
         final errorBody = jsonDecode(response.body);
         throw Exception(
-          errorBody['error'] ??
-              tr(
-                'err.userfront.auth_proxy.consent_accept',
-              ),
+          errorBody['error'] ?? tr('err.userfront.auth_proxy.consent_accept'),
         );
       }
     } finally {
@@ -363,10 +357,7 @@ class AuthProxyService {
       } else {
         final errorBody = jsonDecode(response.body);
         throw Exception(
-          errorBody['error'] ??
-              tr(
-                'err.userfront.auth_proxy.consent_reject',
-              ),
+          errorBody['error'] ?? tr('err.userfront.auth_proxy.consent_reject'),
         );
       }
     } finally {

userfront/lib/core/widgets/language_selector.dart

@@ -15,10 +15,7 @@ class LanguageSelector extends StatelessWidget {
   Widget build(BuildContext context) {
     final current = context.locale.languageCode;
     final items = [
-      DropdownMenuItem(
-        value: 'ko',
-        child: Text(tr('ui.common.language_ko')),
-      ),
+      DropdownMenuItem(value: 'ko', child: Text(tr('ui.common.language_ko'))),
       DropdownMenuItem(
         value: 'en',
         child: Text(tr('ui.common.language_en', fallback: 'English')),