[pytest/dependencies] pytest is declared as a runtime install dependency

[dancasey-ie]

Describe the bug
pytest is listed in install_requires (setup.py line 53) and in requirements.txt (line 7), so it is installed into every environment that installs brightwind — including production/runtime deployments. pytest is a test-time tool only; it is not imported anywhere in the package at runtime.

To Reproduce
Steps to reproduce the behaviour:

1. Create a clean virtual environment.
2. Run pip install brightwind.
3. Run pip list | grep -i pytest.
4. pytest (plus its transitive deps pluggy, iniconfig, etc.) is present.

Expected behavior
Installing brightwind for use (not development) should not pull in pytest. Test-only tooling should live in an optional extra (e.g. dev/test) or a separate requirements-dev.txt.

Additional context
Downstream impact: the BrightHub brightwind-lib-service AWS Lambda image currently bundles pytest 9.1.1 purely as a transitive of brightwind.
Suggested fix: remove pytest from install_requires and requirements.txt, and add extras_require={'dev': ['pytest>=4.1.0']}.