feat: add initial styling and layout for portal views

- Created a global CSS file for consistent styling across the application.
- Implemented the Explore, Home, Topics, and various user views with responsive design.
- Added a Login view with OTP functionality and a Checkout view for order processing.
- Developed a NotFound view for handling 404 errors.
- Established a configuration file for Vite with Tailwind CSS integration.

frontend/portal/src/layout/LayoutAuth.vue

@@ -0,0 +1,5 @@
+<template>
+  <div class="min-h-screen bg-slate-50 flex items-center justify-center p-4">
+    <router-view />
+  </div>
+</template>