[02] Suporte a paginação na pagina de desafios

この issue には説明がありません。

The issue provides no description, files, tests, or entry point; it only requests pagination for the challenges page. Start by locating the challenges-page endpoint and reviewing how comparable endpoints handle pagination. Done means the challenges page supports pagination with behavior consistent with the project’s existing conventions.

索引モデルが issue の本文から書いたものです。