Add GitHub Actions CI to run pytest on push & PR

[Karlitos911]

Summary:
Add a GitHub Actions workflow that installs dependencies and runs pytest on push and pull_request.

What to add:

• .github/workflows/python-tests.yml that:
  • checks out the code
  • sets up Python 3.10
  • installs dependencies via pip install -r requirements.txt
  • runs pytest -q

Acceptance criteria:

• Workflow runs on push and pull_request.
• Tests pass (green check) when tests succeed.

Notes:

• This helps catch regressions automatically on PRs.