Copy tarifas and promos on user registration

When a new user registers with a referral code, their tarifas and promos are now copied from the referring user. Also refactored Usuario_promo and Usuario_tarifa models to use fillable attributes and improved method formatting. Added Swiper CSS/JS to app layout.

resources/views/layouts/app.blade.php

@@ -13,6 +13,7 @@
 
         <link rel="stylesheet" href="https://fonts.googleapis.com/css?family=Poppins">
         <link rel="stylesheet" type="text/css" href="/css/estilos.css" media="screen" />
+        <link rel="stylesheet" href="https://cdn.jsdelivr.net/npm/swiper@12/swiper-bundle.min.css" />
         <!-- Scripts -->
         @vite(['resources/css/app.css', 'resources/js/app.js'])
         <script src="https://cdn.tailwindcss.com"></script>
@@ -35,6 +36,7 @@
 
         </div>
 
+        <script src="https://cdn.jsdelivr.net/npm/swiper@12/swiper-bundle.min.js"></script>
         <script defer src="https://unpkg.com/alpinejs@3.x.x/dist/cdn.min.js"></script>
         @livewireScripts
         <script src="//cdn.jsdelivr.net/npm/sweetalert2@11"></script>