Support new version of python

[github-actions]

New versions of Python are normally released in October.
Follow the checklist below to ensure support for the new version is added,
and drop an old version so we support the most recent 4 versions.

• Change .python-version to be the oldest supported version
• Change requires-python in pyproject.toml to be the oldest supported version
• Change classifiers in template/pyproject.toml.jinja to have all 4 versions
• Change requires-python in template/pyproject.toml.jinja to be the oldest supported version
• Change requires-python in template/uv.lock to be the oldest supported version
• Change python-version in template/*/workflows/ci.yml.jinja to have all 4 versions
• Change first paragraph in template/*/tutorials/installation.md.jinja to be the oldest supported version

[GDYendell]

So this time we are adding 3.14 but keeping 3.11 so that we have 4 versions, @coretl?

[coretl]

Yes, because NEP29 drops a version of python each April (only supporting 3), then adds the new one in October (back to supporting 4), so I though we should once a year support a new one and drop an old one

[DominicOram]

Tangentially related but @jacob720 and I were having a discussion about this and I've made #319