ci: reuse shared Poetry setup for docs

[DiogoRibeiro7]

Use the shared Poetry setup action in the documentation workflow while preserving Python 3.12, Poetry 2.2.1, docs dependency installation, strict MkDocs build, and GitHub Pages deployment.

---

Summary by cubic

Replaces the docs workflow's manual Python and Poetry setup with the shared setup-poetry action from DiogoRibeiro7/git-actions-collection.

The action is configured with Python 3.12, Poetry 2.2.1, and install-deps: "false" so the existing poetry install --with docs step remains the single source for dependency installation.

^{Written for commit c68c55a. Summary will update on new commits.}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!