feat(tutorial): wire tutorial carousel into the first-launch flow

Insert PantallaTutorialAyuda.mostrarSiProcede between the welcome
screen and the recurring what's-new dialog in
_mostrarFlujoPrimerLanzamiento, so the carousel shows once on every
install -- fresh AND existing installs upgrading to this version --
via its own independent one-time flag, without racing either
surface.

lib/app.dart

@@ -16,6 +16,7 @@ import 'pantallas/pantalla_alarmas.dart';
 import 'pantallas/pantalla_alarma_sonando.dart';
 import 'pantallas/pantalla_bienvenida.dart';
 import 'pantallas/pantalla_inicio.dart';
+import 'pantallas/pantalla_tutorial_ayuda.dart';
 import 'pantallas/pantalla_buscar.dart';
 import 'pantallas/pantalla_favoritos.dart';
 import 'pantallas/pantalla_ajustes.dart';
@@ -281,10 +282,20 @@ class _PaginaPrincipalState extends State<_PaginaPrincipal>
   // 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.
+  //
+  // The 9-screen help/tutorial carousel (PantallaTutorialAyuda) runs
+  // BETWEEN the two: after the welcome screen (fresh installs only) and
+  // before the what's-new dialog. Unlike the welcome screen, the tutorial
+  // shows once to EVERY install -- fresh AND existing -- via its own plain
+  // one-time flag (ServicioTutorialAyuda), which is what makes an
+  // already-installed app show it once after updating to this version.
   Future<void> _mostrarFlujoPrimerLanzamiento() async {
     if (mounted) {
       await PantallaBienvenida.mostrarSiProcede(context);
     }
+    if (mounted) {
+      await PantallaTutorialAyuda.mostrarSiProcede(context);
+    }
     await _mostrarOnboardingInicial();
   }