feat(app): restructure to multi-page layout and add content pages

Converts the website from a single-page design with anchor links to a full multi-page application. This change improves site organization, navigation, and scalability.

- Adds new top-level pages: `/news`, `/events`, and `/about`.
- Introduces a new section for the 40th Anniversary at `/40th-anniversary`, including a proposal sub-page.
- Updates the default layout with a new navigation menu, a promotional banner, social links, and page transitions.

app/pages/news/index.vue

@@ -0,0 +1,30 @@
+<template>
+  <UPage>
+    <UPageBody>
+      <UContainer>
+        <UChangelogVersions :versions="newsPost" />
+      </UContainer>
+    </UPageBody>
+  </UPage>
+</template>
+
+<script lang="ts" setup>
+import type { ChangelogVersionProps } from "@nuxt/ui";
+
+const { data: news } = await useAsyncData("news", () =>
+  queryCollection("news").order("date", "DESC").all()
+);
+
+// 将 news 数据转换成 UBlogPosts 可用格式
+const newsPost = computed<ChangelogVersionProps[]>(() =>
+  (news.value || []).map((n: any) => ({
+    title: n.title,
+    description: n.description,
+    image: n.cover,
+    date: n.date,
+    to: n.path, // ✅ 建议加路由跳转
+  }))
+);
+</script>
+
+<style></style>