Feature Request: Access Control for Viewing Articles

## Is your feature request related to a problem? Please describe

Currently, all users can browse all articles without any access restrictions. However, in some cases, we need to limit access so that only specific user groups can view certain articles.

## Describe the solution you'd like

I would like to request a permission-based access control system for browsing articles. Specifically:

Each article should have an associated access group.
Only users belonging to the assigned group should be able to view the article.
Unauthorized users should receive a "Permission Denied" message or be redirected to a different page.

## Describe alternatives you've considered

A few potential solutions could be:

Role-based access control (RBAC): Define roles (e.g., admin, editor, viewer) and associate them with article access.
Group-based permissions: Users can belong to different groups, and articles can be restricted to specific groups.
Tag-based restrictions: Articles could be tagged with access control levels (e.g., "internal only", "public").

## Additional context
This feature would enhance security and provide more control over sensitive or internal articles.
It would be helpful if there were an admin panel where permissions could be managed easily.

Issue ではファイル、テスト、エントリポイントが特定されていないため、まずリポジトリ内で記事の閲覧、ユーザーグループ、権限管理のエントリポイントを見つけます。完了とするには、合意されたアクセス制御設計、記事とグループ間の権限、権限のない閲覧者に対する強制適用、および拒否またはリダイレクト時のレスポンスの定義が必要です。

索引モデルが issue の本文から書いたものです。