fix: move "version" to [project] as per pyproject.toml spec

[metazool]

We tried installing a label-studio-ml-backend project that depends on this SDK using the uv python environment and package management system.

The installation (with uv sync) failed in the same way as this issue; uv has a strict interpretation of the pyproject.toml spec and will bail out if the [project] table has no version information.

• Moves the version property from tools.poetry into project
• Change the dev-dependencies table name to group-dev-dependencies to avoid a deprecation warning
• Update the README to suggest poetry install rather than poetry add label-studio-sdk which also throws an error

uv is getting more uptake and it's worth ensuring your package is installable with it!

Thanks for your work on the project

[metazool]

Example of the traceback we see without this - given a project with "label-studio-ml@git+https://github.com/HumanSignal/label-studio-ml-backend" in its list of dependencies in pyproject.toml

$ uv sync
Using CPython 3.12.7 interpreter at: ...
Creating virtual environment at: .venv
 Updated https://github.com/HumanSignal/label-studio-ml-backend (e86eedf)
 Updated https://github.com/HumanSignal/label-studio-sdk.git (cef5f5d)
  × Failed to download and build `label-studio-sdk @ git+https://github.com/HumanSignal/label-studio-sdk.git`
  ├─▶ Failed to parse: `/home/.../.cache/uv/git-v0/checkouts/73f42ed57643abd9/cef5f5d/pyproject.toml`
  ╰─▶ TOML parse error at line 1, column 1
        |
      1 | [project]
        | ^^^^^^^^^
      `pyproject.toml` is using the `[project]` table, but the required `project.version` field is neither set nor present in the `project.dynamic` list

[metazool]

I added a duplicate version in tools.poetry in order for the pipeline to pass, though this doesn't really feel right.

I'm just told by @jmarshrossney that as of a month ago, poetry has changed its behaviour to be PEP 621 compliant and so this shouldn't be needed with poetry>=2.0.0 :) https://python-poetry.org/blog/announcing-poetry-2.0.0