Require recent python version explicitly

[lisad]

Because the project requierments file includes django 5.2, older versions of python don't work. I figured this out in my environment, but it wasn't obvious, because pip install filters out versions of libraries that don't support your older version of python, so it looked like the error was with django.

There's a couple approaches to this (pyproject.toml? requirements.txt?) but it would be good to use the same approach in our multiple projects

[aborem]

Another approach I've seen is having a .python-version file! I think uv creates the file and sets the version in pyproject.toml by default (so, both).