fix: update getSavedLocale method to return non-nullable Locale type

apps/mobile/packages/core_localization/lib/src/bloc/locale_bloc.dart

@@ -64,16 +64,13 @@ class LocaleBloc extends Bloc<LocaleEvent, LocaleState> {
     LoadLocale event,
     Emitter<LocaleState> emit,
   ) async {
-    final Locale? savedLocale = await getLocaleUseCase();
-    final Locale defaultLocale = getDefaultLocaleUseCase();
+    final Locale savedLocale = await getLocaleUseCase();
     final List<Locale> supportedLocales = getSupportedLocalesUseCase();
 
-    final Locale locale = savedLocale ?? defaultLocale;
-
-    await LocaleSettings.setLocaleRaw(locale.languageCode);
+    await LocaleSettings.setLocaleRaw(savedLocale.languageCode);
 
     emit(LocaleState(
-      locale: locale,
+      locale: savedLocale,
       supportedLocales: supportedLocales,
     ));
   }

apps/mobile/packages/core_localization/lib/src/domain/repositories/locale_repository_interface.dart

@@ -13,7 +13,7 @@ abstract interface class LocaleRepositoryInterface {
   /// Retrieves the saved [locale] from persistent storage.
   ///
   /// Returns `null` if no locale has been previously saved.
-  Future<Locale?> getSavedLocale();
+  Future<Locale> getSavedLocale();
 
   /// Retrieves the default [Locale] for the application.
   Locale getDefaultLocale();

apps/mobile/packages/core_localization/lib/src/domain/usecases/get_locale_use_case.dart

@@ -13,7 +13,7 @@ class GetLocaleUseCase extends NoInputUseCase<Locale?> {
   GetLocaleUseCase(this._repository);
 
   @override
-  Future<Locale?> call() {
+  Future<Locale> call() {
     return _repository.getSavedLocale();
   }
 }