build: drop Python 3.8 support and testing

[joanise]

PR Goal?

Python 3.8 is long EOL, and it prevents us from using uv lock on Windows. There is no value in keeping it anymore, so let's drop it.

Feedback sought?

confirmation we don't need Python 3.8 support anymore

Priority?

normal

Tests added?

all well covered

Confidence?

high

Version change?

not required, but I would like to publish 2.3.2 soon with the recent dependency changes, this drop of 3.8, and the requirements.txt refresh in #493

Related PR

ReadAlongs/Studio#307

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

[roedoejet]

Yes, I think it's fine to drop 3.8 now. thanks @joanise

[github-actions]

CLI load time: 0:00.08
Pull Request HEAD: f6c77d0355668ada80d0555a9151b4551342b613
Imports that take more than 0.1 s:
import time: self [us] | cumulative | imported package