feat(seo): improve SEO configuration and enable SSR

- Enable `ssr: true` in `nuxt.config.ts` for server-side rendering of meta tags.
- Implement `useSeoMeta` in `events/.vue` with fallback logic for Open Graph and Twitter cards.
- Update `content.config.ts` to use `asSeoCollection` for the news collection.
- Migrate event markdown frontmatter to use standardized SEO fields.

content.config.ts

@@ -1,4 +1,5 @@
 import { defineContentConfig, defineCollection, z } from "@nuxt/content";
+import { asSeoCollection } from "@nuxtjs/seo/content";
 
 export default defineContentConfig({
   collections: {
@@ -12,29 +13,31 @@ export default defineContentConfig({
         date: z.coerce.date(),
         location: z.string(),
         cover: z.string().url(),
-        draft: z.boolean().optional().default(false)
+        draft: z.boolean().optional().default(false),
       }),
     }),
     // 新闻集合
-    news: defineCollection({
-      type: "page",
-      source: "news/*.md",
-      schema: z.object({
-        title: z.string(),
-        date: z.coerce.date(),
-        updated: z.coerce.date().optional(),
-        author: z.string(),
-        description: z.string(),
-        cover: z.string().optional(),
-        tags: z.array(z.string()).optional(),
-        category: z.enum(["活动", "通知", "招聘", "博客"]).optional(),
-        highlight: z.boolean().optional(),
-        seoTitle: z.string().optional(),
-        seoDescription: z.string().optional(),
-        ogImage: z.string().optional(),
-        draft: z.boolean().optional().default(false)
-      }),
-    }),
+    news: defineCollection(
+      asSeoCollection({
+        type: "page",
+        source: "news/*.md",
+        schema: z.object({
+          title: z.string(),
+          date: z.coerce.date(),
+          updated: z.coerce.date().optional(),
+          author: z.string(),
+          description: z.string(),
+          cover: z.string().optional(),
+          tags: z.array(z.string()).optional(),
+          category: z.enum(["活动", "通知", "招聘", "博客"]).optional(),
+          highlight: z.boolean().optional(),
+          seoTitle: z.string().optional(),
+          seoDescription: z.string().optional(),
+          ogImage: z.string().optional(),
+          draft: z.boolean().optional().default(false),
+        }),
+      })
+    ),
     // 名人堂
     hallOfFames: defineCollection({
       type: "page",