Replace Poetry with uv for dependency management

[syssi]

Summary

• Migrate pyproject.toml from [tool.poetry] to PEP 621 [project] table
• Switch build backend from poetry-core to hatchling
• Replace [tool.poetry.group.dev] with PEP 735 [dependency-groups]
• Move mypy type stubs from .pre-commit-config.yaml additional_dependencies into the dev dependency group
• Replace poetry.lock with uv.lock (98 packages resolved)
• Update CI to use astral-sh/setup-uv instead of pip install poetry
• Update RELEASING.md with uv build / uv publish commands

Migration notes

uv sync --extra docs replaces poetry install --extras docs
uv sync --all-extras replaces poetry install --all-extras
uv run <cmd> replaces poetry run <cmd>

Test plan

• CI linting job passes (uv sync --extra docs + pre-commit)
• CI test matrix passes on Python 3.11, 3.12, 3.13 across ubuntu/macos/windows
• uv build produces a valid wheel and sdist

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 83.49%. Comparing base (1374cfd) to head (c82c123).

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #2079   +/-   ##
=======================================
  Coverage   83.49%   83.49%           
=======================================
  Files         199      199           
  Lines       19519    19522    +3     
  Branches     1058     1058           
=======================================
+ Hits        16297    16300    +3     
  Misses       3036     3036           
  Partials      186      186           

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[rytilahti]

I have not tested running any of this, but it looks good on the surface. Thanks @syssi!