feat(localization): add localization generation step and update l10n configuration

flutter/Dockerfile

@@ -8,6 +8,9 @@ RUN flutter pub get
 
 COPY . .
 
+# Generate localizations (ARB -> Dart) before the main build.
+RUN flutter gen-l10n
+
 # Inject API base URL at build time via --dart-define.
 # Default to same-origin /api to avoid mixed-content in HTTPS deployments.
 ARG API_BASE_URL=/api

flutter/l10n.yaml

@@ -1,3 +1,5 @@
 arb-dir: lib/l10n
 template-arb-file: app_en.arb
 output-localization-file: app_localizations.dart
+output-dir: lib/l10n/generated
+synthetic-package: false

flutter/lib/core/l10n/l10n.dart

@@ -1,5 +1,7 @@
 import 'package:flutter/widgets.dart';
-import 'package:flutter_gen/gen_l10n/app_localizations.dart';
+import 'package:recipe_flutter/l10n/generated/app_localizations.dart';
+
+export 'package:recipe_flutter/l10n/generated/app_localizations.dart';
 
 extension AppLocalizationsX on BuildContext {
   AppLocalizations get l10n => AppLocalizations.of(this)!;