Review Nuxt SEO integration options

Check against https://certificates.dev/blog/seo-in-nuxt-with-at-nuxtjsseo

Start by reading the linked certificates.dev article and comparing its Nuxt SEO approach with the repository's current setup. The issue names no files, tests, or concrete change, so the intended outcome and definition of done need to be clarified before implementation.

索引モデルが issue の本文から書いたものです。