perf(userfront): optimize login web loading

userfront/lib/core/i18n/locale_registry.dart

@@ -31,6 +31,22 @@ class LocaleRegistry {
   static final Set<String> _localeCodes = <String>{};
   static bool _initialized = false;
 
+  static void primeWithDefaults({
+    Iterable<String> localeCodes = const ['en', 'ko'],
+  }) {
+    if (_localeCodes.isNotEmpty) {
+      return;
+    }
+    _localeCodes.addAll(
+      localeCodes
+          .map((code) => code.toLowerCase().replaceAll('_', '-'))
+          .where(_isValidLocaleCode),
+    );
+    if (_localeCodes.isEmpty) {
+      _localeCodes.add(_safeFallbackLocaleCode);
+    }
+  }
+
   static Future<void> initialize({AssetBundle? assetBundle}) async {
     if (_initialized) {
       return;

userfront/lib/core/theme/app_theme.dart

@@ -42,11 +42,7 @@ ThemeData buildDarkTheme() {
 
 ThemeData _buildTheme(ColorScheme colorScheme) {
   final isDark = colorScheme.brightness == Brightness.dark;
-  final base = ThemeData(
-    useMaterial3: true,
-    colorScheme: colorScheme,
-    fontFamily: 'NotoSansKR',
-  );
+  final base = ThemeData(useMaterial3: true, colorScheme: colorScheme);
 
   return base.copyWith(
     scaffoldBackgroundColor: colorScheme.surfaceContainerLowest,