Deploy docs site with Hugo via GitHub Actions

[oschwald]

Summary

Migrates the Pages index from Jekyll on gh-pages to a Hugo build that
publishes back onto gh-pages from GitHub Actions. All CSS is now
inlined in the layout template — no external CDN dependencies.

• Hugo site lives under docs/ on main and mounts README.md as the
  home page
• A small pill nav links from the overview to the phpDocumentor output
  at /doc/latest/
• .github/workflows/pages.yml builds with mise run build-docs and
  pushes to gh-pages via peaceiris/actions-gh-pages with
  keep_files: true, so every /doc/vX.Y.Z/ subtree stays untouched
• dev-bin/release.sh no longer regenerates the Jekyll index.md;
  the phpDocumentor-publishing block is unchanged

Same design as MaxMind-DB PR #221.

For STF-448.

Post-merge steps

1. Verify the live site at https://maxmind.github.io/minfraud-api-php/
   and a sample /doc/latest/ still loads after the next workflow run
2. In a separate commit on gh-pages, drop the legacy Jekyll source
   files

Pages source stays on gh-pages — no Terraform change for this repo.

Test plan

• mise run build-docs succeeds with no warnings
• Rendered <title>, <h1>, and pill nav are correct
• No static-gh.maxmind.com references in the new site
• Build job passes in CI (push step only runs on main)
• After merge, confirm the workflow pushes successfully to gh-pages
  and /doc/vX.Y.Z/ subtrees are preserved

🤖 Generated with Claude Code

[gemini-code-assist]

Code Review

This pull request migrates the project's documentation system to Hugo, replacing a manual script that generated the index page from the README. It introduces a new Hugo configuration, layouts, and mise tasks for building and serving the documentation site. Feedback includes improving accessibility by adding aria-current="page" to active navigation links and ensuring the local development server uses a consistent base URL to prevent broken links.

[gemini-code-assist]

For better accessibility, add aria-current="page" to the active navigation link. This helps screen reader users identify the current page within the navigation menu.

Suggested change

	<a href="{{ .Site.Home.RelPermalink }}"{{ if .IsHome }} class="active"{{ end }}>Overview</a>
	<a href="{{ .Site.Home.RelPermalink }}"{{ if .IsHome }} class="active" aria-current="page"{{ end }}>Overview</a>

[gemini-code-assist]

The "API documentation" link in the template uses relURL, which prepends the path from the production baseURL (e.g., /minfraud-api-php/). When running the dev server locally, this link will be broken unless the server is configured with the same base path. Adding the --baseURL flag ensures the local development environment matches the production path structure.

Suggested change

	run = "hugo server --source docs"
	run = "hugo server --source docs --baseURL http://localhost/minfraud-api-php/"