docs: Fix double logo on PyPI

[cpswan]

PyPI is showing two Atsign logos because of light and dark mode in README.md

- What I did

• Added README.PyPI.md with single logo (per what we did with at_python publishing to atsdk)
• Ruff linting for Python packages
• Automated bumping of poetry version for Dependabot PRs
• Removed old Python example code

- How I did it

Mostly copy/paste from at_python

- How to verify it

Check TestPyPI after merging

- Description for the changelog

docs: Fix double logo on PyPI