Use uv pip for base dependency installs

[richarms]

This migrates the shared build path from install_pinned.py to uv pip. Base images now preinstall a pinned uv and use uv pip compile followed by uv pip install --no-deps and uv pip check to build their Python environments. Jenkins package builds follow the same pattern: compile each requirements file against the checked-out katsdpdockerbase base/GPU constraints, install the generated lock, and run uv pip check.

This keeps the migration focused on replacing the custom installer with standard uv tooling; cleanup of legacy package requirement files that still embed katsdpdockerbase -c/-d lines will be handled separately.