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/views/misc/NotFoundView.vue

@@ -0,0 +1,16 @@
+<template>
+  <div class="min-h-screen flex items-center justify-center bg-slate-50">
+    <div class="text-center">
+      <div class="mb-6">
+         <!-- Use an image or illustration here -->
+         <i class="pi pi-compass text-6xl text-slate-300"></i>
+      </div>
+      <h1 class="text-4xl font-bold text-slate-900 mb-4">404</h1>
+      <p class="text-xl text-slate-600 mb-8">抱歉，您访问的页面走丢了。</p>
+      <div class="flex justify-center gap-4">
+        <router-link to="/" class="px-6 py-3 bg-primary-600 text-white rounded-lg hover:bg-primary-700 transition-colors">返回首页</router-link>
+        <button @click="$router.back()" class="px-6 py-3 border border-slate-300 text-slate-700 rounded-lg hover:bg-slate-50 transition-colors">返回上一页</button>
+      </div>
+    </div>
+  </div>
+</template>