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.

nuxt.config.ts

@@ -29,28 +29,46 @@ export default defineNuxtConfig({
       ],
       meta: [
         // 基础 SEO
-        { name: "description", content: "永平中学校友会官网 - 连接校友，共享资源，传承母校精神。" },
-        { name: "keywords", content: "永平中学, 校友会, 永平中学校友, 永平校友, 同学会" },
+        {
+          name: "description",
+          content: "永平中学校友会官网 - 连接校友，共享资源，传承母校精神。",
+        },
+        {
+          name: "keywords",
+          content: "永平中学, 校友会, 永平中学校友, 永平校友, 同学会",
+        },
         { name: "author", content: "永平中学校友会" },
         { name: "viewport", content: "width=device-width, initial-scale=1" },
 
         // Open Graph（Facebook/LinkedIn）
         { property: "og:title", content: "永平中学校友会" },
-        { property: "og:description", content: "永平中学校友会官网 - 连接校友，共享资源，传承母校精神。" },
+        {
+          property: "og:description",
+          content: "永平中学校友会官网 - 连接校友，共享资源，传承母校精神。",
+        },
         { property: "og:type", content: "website" },
         { property: "og:url", content: "https://yphsalumni.org" }, // ✅ 换成你网站的真实域名
-        { property: "og:image", content: "https://yphsalumni.org/hero-image.jpg" }, // ✅ 上传一张封面图
+        {
+          property: "og:image",
+          content: "https://yphsalumni.org/hero-image.jpg",
+        }, // ✅ 上传一张封面图
 
         // Twitter Card
         { name: "twitter:card", content: "summary_large_image" },
         { name: "twitter:title", content: "永平中学校友会" },
-        { name: "twitter:description", content: "连接校友，共享资源，传承母校精神。" },
-        { name: "twitter:image", content: "https://yphsalumni.org/hero-image.jpg" },
+        {
+          name: "twitter:description",
+          content: "连接校友，共享资源，传承母校精神。",
+        },
+        {
+          name: "twitter:image",
+          content: "https://yphsalumni.org/hero-image.jpg",
+        },
       ],
     },
   },
   site: {
     url: "https://yphsalumni.com",
-    name: "永中校友会 YPHS Alumni"
-  }
-});
+    name: "永中校友会 YPHS Alumni",
+  },
+});