chore: migrate legacy pages and utilities to nuxt

frontend_nuxt/pages/404.vue

@@ -0,0 +1,33 @@
+<template>
+  <div class="not-found-page">
+    <h1>404 - 页面不存在</h1>
+    <p>你访问的页面不存在或已被删除</p>
+    <router-link to="/">返回首页</router-link>
+  </div>
+</template>
+
+<script>
+export default {
+  name: 'NotFoundPageView'
+}
+</script>
+
+<style scoped>
+.not-found-page {
+  display: flex;
+  flex-direction: column;
+  align-items: center;
+  height: 100%;
+  text-align: center;
+  background-color: var(--background-color);
+}
+
+.not-found-page h1 {
+  margin-bottom: 20px;
+}
+
+.not-found-page a {
+  color: var(--primary-color);
+  text-decoration: underline;
+}
+</style>