Test updated release workflow - Version 5.2.6a1 release

[intgr]

Testing, because recent PRs have touched the release workflow.

Using alpha version in case anything goes wrong -- so users won't be updated automatically.

• Use same uv workspace for django-stubs-ext also #2857
• Update release documentation, workflow and build-and-check job to uv #2846

[intgr]

It worked!

• https://pypi.org/project/django-stubs-ext/5.2.6a1/
• https://pypi.org/project/django-stubs/5.2.6a1/

There are some warnings from the release workflow, but harmless https://github.com/typeddjango/django-stubs/actions/runs/18260529316/job/51987842061

No file matched to [/home/runner/work/django-stubs/django-stubs/**/*requirements*.txt,/home/runner/work/django-stubs/django-stubs/**/*requirements*.in,/home/runner/work/django-stubs/django-stubs/**/*constraints*.txt,/home/runner/work/django-stubs/django-stubs/**/*constraints*.in,/home/runner/work/django-stubs/django-stubs/**/pyproject.toml,/home/runner/work/django-stubs/django-stubs/**/uv.lock,/home/runner/work/django-stubs/django-stubs/**/*.py.lock]. The cache will never get invalidated. Make sure you have checked out the target repository and configured the cache-dependency-glob input correctly.