build(deps): bump the docs-dependencies group across 1 directory with 3 updates

Bumps the docs-dependencies group with 3 updates in the /docs directory: [sphinx](https://github.com/sphinx-doc/sphinx), [sphinx-autodoc-typehints](https://github.com/tox-dev/sphinx-autodoc-typehints) and [furo](https://github.com/pradyunsg/furo).


Updates `sphinx` from 8.2.3 to 9.1.0
- [Release notes](https://github.com/sphinx-doc/sphinx/releases)
- [Changelog](https://github.com/sphinx-doc/sphinx/blob/master/CHANGES.rst)
- [Commits](sphinx-doc/sphinx@v8.2.3...v9.1.0)

Updates `sphinx-autodoc-typehints` from 3.1.0 to 3.6.0
- [Release notes](https://github.com/tox-dev/sphinx-autodoc-typehints/releases)
- [Commits](tox-dev/sphinx-autodoc-typehints@3.1.0...3.6.0)

Updates `furo` from 2025.9.25 to 2025.12.19
- [Release notes](https://github.com/pradyunsg/furo/releases)
- [Changelog](https://github.com/pradyunsg/furo/blob/main/docs/changelog.md)
- [Commits](pradyunsg/furo@2025.09.25...2025.12.19)

---
updated-dependencies:
- dependency-name: sphinx
  dependency-version: 9.1.0
  dependency-type: direct:production
  update-type: version-update:semver-major
  dependency-group: docs-dependencies
- dependency-name: sphinx-autodoc-typehints
  dependency-version: 3.6.0
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: docs-dependencies
- dependency-name: furo
  dependency-version: 2025.12.19
  dependency-type: direct:production
  update-type: version-update:semver-minor
  dependency-group: docs-dependencies
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

docs/requirements.txt

@@ -1,4 +1,4 @@
-Sphinx==8.2.3
-sphinx-autodoc-typehints==3.1.0
-furo==2025.9.25
+Sphinx==9.1.0
+sphinx-autodoc-typehints==3.6.0
+furo==2025.12.19
 myst-parser==4.0.1