Update furo requirement from >=2024.1.29 to >=2025.12.19

Updates the requirements on [furo](https://github.com/pradyunsg/furo) to permit the latest version.
- [Release notes](https://github.com/pradyunsg/furo/releases)
- [Changelog](https://github.com/pradyunsg/furo/blob/main/docs/changelog.md)
- [Commits](https://github.com/pradyunsg/furo/compare/2024.01.29...2025.12.19)

---
updated-dependencies:
- dependency-name: furo
  dependency-version: 2025.12.19
  dependency-type: direct:production
...

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

docs/requirements.txt

@@ -13,7 +13,7 @@ sphinx-autodoc-typehints>=1.25.0
 sphinx-sitemap>=2.6.0
 
 # Alternative modern theme (optional)
-furo>=2024.1.29
+furo>=2025.12.19
 
 # Main package dependencies (needed for autodoc to import modules)
 zstandard>=0.19.0,<1.0.0