Update all references to Python 3.11 to use Python 3.14 to match
the pyproject.toml requires-python = ">=3.14" setting:
- bin/lock_pkgs.sh: uv venv --python 3.14
- .github/workflows/test.yml: python matrix and PDM version
- .github/workflows/pip.yml: PYTHON_VERSION env var
- Dockerfile: comment and example FROM line
- Issue templates: example version output