Migrate Python tooling from pip-tools/tox to uv

[hf-krechan]

Summary

• Move dev-tool groups (tests, linting, type_check, spell_check, coverage, formatting) from project.optional-dependencies to PEP 735 [dependency-groups]; also moves packaging (build/twine) there since it's maintainer tooling, not a user-facing extra. dev group aggregates everything + pre-commit, replacing the removed pip-tools dependency.
• Remove tox.ini and requirements.txt; add uv.lock (generated via uv lock). Set [tool.uv] default-groups = [] so isolated CI jobs (uv sync --group X) don't implicitly pull in the whole dev group.
• Update all .github/workflows/*.yml to install uv via astral-sh/setup-uv@v9.0.0 and run uv sync --group X + uv run <tool> instead of pip install tox + tox -e X (also drops the separate actions/setup-python step, since setup-uv pins the interpreter).
• Rewrite the README bootstrap section: drop the toxbase Windows/Unix setup instructions in favor of uv sync --group dev, and point PyCharm/VS Code interpreter instructions at .venv instead of .tox/dev.
• No application code changes — tooling/config/CI/docs only.

Test plan

• uv lock / uv sync --group dev succeed
• uv run pytest passes
• Spot-checked isolated groups work: linting (pylint 10/10), type_check (mypy strict, clean), spell_check (codespell, clean), coverage (100%, report generates), formatting (black/isort clean), packaging (build + twine check pass)
• pre-commit hooks run clean on the commit

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