Upgrade Python version in project files

Update the Python version referenced in project metadata and packaging files to a target version. Updates Pipfile (python_version / python_full_version), pyproject.toml ([project] requires-python and Poetry's [tool.poetry.dependencies] python), setup.py and setup.cfg (python_requires), .python-version files, and Ruff's target-version (in [tool.ruff], ruff.toml, and .ruff.toml). When a lock file (uv.lock or Pipfile.lock) is present, it is regenerated natively to match, without executing the package manager or requiring one on PATH. Only references older than the target are changed; a file already on a newer version is left as-is. Dockerfiles, CI workflows, and infrastructure files are handled by the other recipes that UpgradePythonVersion composes, and requirements.txt is not modified because it pins package versions, not the interpreter version.