fix: Restrict Python version to <3.13
- fixes #1539
- enforce Python <3.13
- add back poetry.lock which seems to have been removed accidentally (?) in 2121316 and added unintentionally (?) to the .gitignore in #1482
- ~add all supported python versions to CI tests~
I added back the poetry.lock file which seems to have been accidentally deleted (at least I couldn't find any PR or commit message explaining why it's gone) ~and also added python 3.9 and 3.11 to the CI checks since they're both supported versions (also not sure why they're not there already, but feel free to revert the last commit if there's some reason).~ [this was removed from the development branch so i undid the change]

no no no, why do you want to support an ancient version of python... just ask codex to fix it wiht python 3.13 ez
no no no, why do you want to support an ancient version of python...
See #1539