feat(localization): Implement Swedish localization and error messages

- Added localization support for Swedish and English languages.
- Integrated localized strings for user messages in the API error mapper.
- Updated UI components to use localized strings for labels and messages.
- Ensured all error messages are context-aware and utilize the localization framework.
- Created regression test to prevent common ASCII fallbacks in Swedish UI text.

flutter/lib/main.dart

@@ -1,5 +1,8 @@
 import 'package:flutter/material.dart';
+import 'package:flutter_localizations/flutter_localizations.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
+
+import 'core/l10n/l10n.dart';
 import 'core/router/app_router.dart';
 
 void main() {
@@ -13,11 +16,19 @@ class RecipeApp extends ConsumerWidget {
   Widget build(BuildContext context, WidgetRef ref) {
     final router = ref.watch(appRouterProvider);
     return MaterialApp.router(
-      title: 'Recipe App',
+      onGenerateTitle: (context) => context.l10n.appTitle,
       theme: ThemeData(
         colorScheme: ColorScheme.fromSeed(seedColor: Colors.green),
         useMaterial3: true,
       ),
+      localizationsDelegates: const [
+        AppLocalizations.delegate,
+        GlobalMaterialLocalizations.delegate,
+        GlobalWidgetsLocalizations.delegate,
+        GlobalCupertinoLocalizations.delegate,
+      ],
+      supportedLocales: AppLocalizations.supportedLocales,
+      locale: const Locale('sv'),
       routerConfig: router,
     );
   }