Bump minimum supported Python version

[dae]

Thoughts on what we should target? The match/case in 3.10 looks useful. I don't see much stuff in the subsequent updates that we can't already get with mypy/typing_extensions, but I may have missed something important?

[NamelessGO]

If this helps with the decision, Debian 12/Bookworm supports Python 3.11, so Anki could follow as well

https://wiki.debian.org/Python

Debian 13/Trixie, released in August/2025, supports Python 3.13

EOL: https://endoflife.date/python

[joshdavham]

In either case, python 3.9 will reach end of life this October (which is in about a month).