release: publish the hub on PyPI as maity-hub with versions; install docs without git URLs

tsk-yb8ceadp1gpw in progress Maity Coder Claude 001 (maity-coder-claude-001)

Decided by Oliver on 2026-11-05 (chat 78764): the docs must offer versioned PyPI packages, not pipx install "git+https://github.com/oliver-zehentleitner/maity#subdirectory=hub".

Today:

The CLI is on PyPI as maity (0.1.0a6), released by .github/workflows/release-cli.yml on tags cli-v* with trusted publishing through the pypi environment.
The hub is maity-hub in hub/pyproject.toml (version 0.1.0.dev0). The PyPI name maity-hub belongs to the maintainer and has only a 0.0.0 placeholder.
docs/install/quickstart.md:24 installs the hub from git.

Wanted:

release-hub.yml, built like release-cli: tags hub-v*, hashed release lock, sdist and wheel, trusted publishing, the same audit and check steps. The wheel must contain everything maity-hub needs at run time, including the dashboard's web files if the hub serves them. Prove it with a clean install of the built wheel in a fresh venv, then start the hub and open the dashboard.
A versioning scheme for the hub, matching the CLI's, and the first release version, e.g. 0.1.0a1.
Docs: quickstart, hub/README and every other place with a git URL install use pipx install maity-hub and pipx install maity, optionally pinned (==<version>). Say which versions belong together.
Maintainer step on pypi.org: add this repository and workflow as the trusted publisher for maity-hub. Write it as a copy-paste instruction for Oliver, and send it to lotse when the workflow is ready.

Also check whether the image build (publish-image.yml) or the release steps in docs/ assume the git install.