Add `project.version` to pyproject.toml to allow uvx to install KRR

[JJGadgets]

Describe the bug
uv (via mise) fails to install KRR due to missing project.version field in pyproject.toml file.

To Reproduce
Steps to reproduce the behavior:

1. Use uvx to install KRR
2. Error shows

Expected behavior
Successful uvx install.

Screenshots

Are you interested in contributing a fix for this?
Yes. Haven't understood the release workflow yet to open a PR, thus issue first.

Desktop (please complete the following information):

• OS: Linux
• Version: v1.24.0

Additional context
Add any other context about the problem here.

[aantn]

Thanks, the best fix is probably updating poetry version to 2.0+ and migrating to use [project] instead of the poetry specific fields. (See https://python-poetry.org/blog/announcing-poetry-2.0.0/)