Docs: Set up a Docs Site for ApiEndpoints using GitHub Pages

Model this on the Ardalis.Specification approach:

- https://github.com/ardalis/Specification/tree/main/docs
- https://ardalis.github.io/Specification/
- https://docs.github.com/en/pages/getting-started-with-github-pages/creating-a-github-pages-site

Review the linked Ardalis.Specification docs directory and rendered site, then compare their structure with the ApiEndpoints repository. Read the GitHub Pages setup guidance to determine the required documentation and publishing configuration. Done means ApiEndpoints has a documented site structure and a working GitHub Pages deployment comparable to the reference.

Written by the indexing model from the issue text.