Docs shaping

[domna]

This

• reshapes the docs to use the more modern mkdocs material
• reorders according to the diataxis framework to improve structure and maintainability of the docs

Viewing the docs

After syncing the new dependencies (e.g., with pip install -e '.[dev,docs]' or uv sync --extra dev --extra docs) the docs can be viewed with

mkdocs serve --livereload

or uv run mkdocs serve --livereload when using uv.