ci: add ruff check to workflow

[rajanpanth]

Summary

• Adds poetry run ruff check . to the existing build+test workflow
• Runs Ruff only once on the Python 3.11 matrix entry to avoid repeating the same repository lint on every Python version

Closes #292.

Testing

• Not run locally: Poetry is not installed in the current environment.

Notes

AI assistance was used to help prepare this change.

[NoodlesNZ]

Currently poetry run ruff check . gives 108 errors on the master branch. This would block other PRs from merging cleanly until the errors are fixed. While this is a good idea, we probably need to delay this for now