Tutor and plugins should drop compatibility with Python 3.9 and ensure compatibility with Python 3.14

[regisb]

Is your feature request related to a problem? Please describe.

Python 3.9 has reached end of life, and Python 3.13 and 3.14 are now out: https://endoflife.date/python

Describe the solution you'd like

We should be able to run Tutor and all plugins in the latest versions of Python:

pyenv install 3.13
pyenv install 3.14
~/.pyenv/versions/3.13.3/bin/python -m pip install tutor[full]
~/.pyenv/versions/3.14.0/bin/python -m pip install tutor[full]
tutor local launch

Note that we will have to upgrade the CI from 3.9/3.12 to 3.10/3.14.