Replace setup.py with pyproject.toml, add pipeline CLI entrypoints

[sbiquard]

Replaces setup.py with pyproject.toml (hatchling backend) and adds soopercool-* console-script entrypoints for the pipeline scripts, so they're runnable without python pipeline/foo.py.

List of changes:

• Wrap pipeline/ scripts in cli() functions
• Add __init__.py files to package so entrypoints resolve
• Make sibling imports relative
• Unused scripts commented out in [project.scripts] table
• Add missing scikit-learn dependency
• Swap sotodlib for stdlib logging in precompute_cov_couplings.py, using the same loglevel (warning)
• Drop requirements.txt, deps now live in pyproject.toml
• CI: python setup.py install becomes pip install .

[sbiquard]

pip-installed console scripts need a callable without any arguments (entry = "module:func" calls bare func()). Wrapping the argument parser and main(args) call in a cli() function called from the if __name__ == "__main__": block is the most minimal fix to apply and it preserves main's signature.