Switch GitHub Actions workflows (`docs`, `mirror`, `pypi`) from `ubuntu-latest` to `self-hosted` runners.
This change also updates the Python environment setup in `docs.yml` and `pypi.yml` to manually create and activate a virtual environment (`venv`). This provides more control over the Python environment on self-hosted machines and ensures dependencies are isolated.
Enables automatic documentation deployment to GitHub Pages when documentation files are modified on the master branch.
Triggers on changes to docs directory or mkdocs.yml configuration file to ensure documentation stays current with code changes.
