fix(bienvenida): wire the welcome screen into the first-launch flow

lib/app.dart

@@ -14,6 +14,7 @@ import 'l10n/gen/app_localizations.dart';
 import 'modelos/alarma_musical.dart';
 import 'pantallas/pantalla_alarmas.dart';
 import 'pantallas/pantalla_alarma_sonando.dart';
+import 'pantallas/pantalla_bienvenida.dart';
 import 'pantallas/pantalla_inicio.dart';
 import 'pantallas/pantalla_buscar.dart';
 import 'pantallas/pantalla_favoritos.dart';
@@ -108,7 +109,10 @@ class _PaginaPrincipalState extends State<_PaginaPrincipal>
   EstadoRadio? _estadoSuscrito;
   bool _alarmaInicialProcesada = false;
   bool _alarmaSonandoActiva = false;
-  bool _onboardingInicialSolicitado = false;
+  // WU17b: renamed from `_onboardingInicialSolicitado` — this single guard
+  // now covers the whole first-launch sequence (welcome screen, then the
+  // pre-existing what's-new dialog), not only the dialog.
+  bool _flujoPrimerLanzamientoSolicitado = false;
   String? _alarmaSonandoId;
   Locale? _localeAlarmasConfigurado;
 
@@ -191,9 +195,9 @@ class _PaginaPrincipalState extends State<_PaginaPrincipal>
       _alarmaInicialProcesada = true;
       unawaited(_procesarAlarmaInicial(alarmas));
     }
-    if (!_onboardingInicialSolicitado) {
-      _onboardingInicialSolicitado = true;
-      unawaited(_mostrarOnboardingInicial());
+    if (!_flujoPrimerLanzamientoSolicitado) {
+      _flujoPrimerLanzamientoSolicitado = true;
+      unawaited(_mostrarFlujoPrimerLanzamiento());
     }
   }
 
@@ -278,6 +282,19 @@ class _PaginaPrincipalState extends State<_PaginaPrincipal>
     }
   }
 
+  // WU17b: runs the welcome screen's once-ever check BEFORE the recurring
+  // what's-new dialog, so the two never show at the same time. The welcome
+  // screen (PantallaBienvenida) is the genuine first-run surface; the
+  // pre-existing PluriOnboardingDialog is an unrelated "what's new"/help
+  // modal that keeps its own independent per-version due-or-not logic,
+  // completely unchanged by this sequencing.
+  Future<void> _mostrarFlujoPrimerLanzamiento() async {
+    if (mounted) {
+      await PantallaBienvenida.mostrarSiProcede(context);
+    }
+    await _mostrarOnboardingInicial();
+  }
+
   Future<void> _mostrarOnboardingInicial() async {
     await Future<void>.delayed(const Duration(milliseconds: 900));
     if (!mounted || _alarmaSonandoActiva) return;