Move jupyter-ai on PyPI to Project Jupyter organization, use trusted publishers

[krassowski]

Problem

Currently jupyter-ai on PyPI is:

• not using Trusted Publishers
• not under Project Jupyter
• has a sole maintainer listed on PyPI

Proposed Solution

• Move to Project Jupyter https://pypi.org/org/jupyter/
• Setup Trusted Publisher for GitHub Workflow using jupyter-releaser

Additional context

• I touched upon this Deprecate old packages and hide them from the extension manager #333 (comment)
• We will need trusted publishers + attestations to verify extension provenance in Extension Manager, see discussion in Fix order of extensions in PyPI Extension Manager jupyterlab#17266
• https://docs.pypi.org/trusted-publishers/adding-a-publisher/
• https://jupyter-releaser.readthedocs.io/en/stable/how_to_guides/convert_repo_from_repo.html