fix(i18n): normalize translations and fallbacks

lib/widgets/pluri_onboarding_dialog.dart

@@ -1,5 +1,6 @@
 import 'package:flutter/material.dart';
 
+import '../l10n/gen/app_localizations.dart';
 import '../servicios/servicio_contenido_app.dart';
 import 'pluri_glass_surface.dart';
 import 'pluri_markdown.dart';
@@ -41,7 +42,7 @@ class _PluriOnboardingContent extends StatelessWidget {
 
   @override
   Widget build(BuildContext context) {
-    final labels = _labels(Localizations.localeOf(context).languageCode);
+    final l10n = AppLocalizations.of(context);
     final size = MediaQuery.sizeOf(context);
     return Dialog(
       insetPadding: const EdgeInsets.all(16),
@@ -80,14 +81,14 @@ class _PluriOnboardingContent extends StatelessWidget {
                   const SizedBox(width: 14),
                   Expanded(
                     child: Text(
-                      labels.title,
+                      l10n.onboardingTitle,
                       style: Theme.of(context).textTheme.titleLarge?.copyWith(
                         fontWeight: FontWeight.w900,
                       ),
                     ),
                   ),
                   IconButton(
-                    tooltip: labels.close,
+                    tooltip: l10n.onboardingCloseTooltip,
                     onPressed: () => Navigator.of(context).pop(),
                     icon: const Icon(Icons.close_rounded),
                   ),
@@ -102,7 +103,7 @@ class _PluriOnboardingContent extends StatelessWidget {
                     if (contenido.notas.isNotEmpty) ...[
                       const SizedBox(height: 18),
                       Text(
-                        labels.news,
+                        l10n.onboardingNewsTitle,
                         style: Theme.of(context).textTheme.titleLarge?.copyWith(
                           fontWeight: FontWeight.w900,
                         ),
@@ -131,7 +132,7 @@ class _PluriOnboardingContent extends StatelessWidget {
                 child: FilledButton.icon(
                   onPressed: () => Navigator.of(context).pop(),
                   icon: const Icon(Icons.check_rounded),
-                  label: Text(labels.start),
+                  label: Text(l10n.onboardingStartAction),
                 ),
               ),
             ],
@@ -141,58 +142,3 @@ class _PluriOnboardingContent extends StatelessWidget {
     );
   }
 }
-
-_OnboardingLabels _labels(String languageCode) {
-  return switch (languageCode) {
-    'es' => const _OnboardingLabels(
-      title: 'Bienvenido a PluriWave',
-      news: 'Novedades',
-      start: 'Empezar',
-      close: 'Cerrar',
-    ),
-    'fr' => const _OnboardingLabels(
-      title: 'Bienvenue sur PluriWave',
-      news: 'Nouveautés',
-      start: 'Commencer',
-      close: 'Fermer',
-    ),
-    'de' => const _OnboardingLabels(
-      title: 'Willkommen bei PluriWave',
-      news: 'Neuigkeiten',
-      start: 'Starten',
-      close: 'Schließen',
-    ),
-    'it' => const _OnboardingLabels(
-      title: 'Benvenuto in PluriWave',
-      news: 'Novità',
-      start: 'Inizia',
-      close: 'Chiudi',
-    ),
-    'pt' => const _OnboardingLabels(
-      title: 'Bem-vindo ao PluriWave',
-      news: 'Novidades',
-      start: 'Começar',
-      close: 'Fechar',
-    ),
-    _ => const _OnboardingLabels(
-      title: 'Welcome to PluriWave',
-      news: 'What’s new',
-      start: 'Start',
-      close: 'Close',
-    ),
-  };
-}
-
-class _OnboardingLabels {
-  const _OnboardingLabels({
-    required this.title,
-    required this.news,
-    required this.start,
-    required this.close,
-  });
-
-  final String title;
-  final String news;
-  final String start;
-  final String close;
-}