Minimum Python and recommended installation docs

[oberstet]

Feature Description

Checklist

Update docs to reflect minimum Python 3.11 version, eg

https://autobahn.readthedocs.io/en/v25.12.2/overview.html

"... for Python 3.9+ ..." should be "... for Python 3.11+ ..."

and installation docs

https://autobahn.readthedocs.io/en/v25.12.2/installation.html

should reflect and document the comprehensive set of binary native wheels we now publish as the recommended way to install

https://pypi.org/project/autobahn/#files

• I have searched existing issues to avoid duplicates
• I have described the problem clearly
• I have provided use cases
• I have considered alternatives
• I have assessed impact and breaking changes