chore(deps): update all non-major dependencies - #167

The new Python 3.15 slim image cannot build the locked cffi dependency, blocking the Docker build; the earlier minimum-Python coverage finding also remains open.

The PR refreshes dependency pins across the GitHub workflows, package configuration, and local container setup. It moves CI and publishing to Python 3.15, updates uv and the Python development/build tools, and advances the Dragonfly image.