feat(seo): implement SEO enhancements and social media embeds

This commit introduces significant SEO improvements and enhances content embedding capabilities.

- Integrates `@nuxtjs/seo`, `@nuxtjs/sitemap`, and `@nuxtjs/robots` to boost search engine visibility.
- Configures global meta tags, including Open Graph and Twitter Cards, for richer social media sharing.
- Adds support for embedding YouTube and Facebook content directly within markdown pages.
- Introduces a new `TikTokEmbed` component for future use.

package.json

@@ -13,6 +13,9 @@
     "@nuxt/content": "3.7.1",
     "@nuxt/image": "1.11.0",
     "@nuxt/ui": "4.0.0",
+    "@nuxtjs/robots": "5.5.5",
+    "@nuxtjs/seo": "3.2.2",
+    "@nuxtjs/sitemap": "7.4.7",
     "@tailwindcss/vite": "^4.1.13",
     "better-sqlite3": "^12.4.1",
     "element-plus": "^2.11.4",