Fix namespace library generation and audit target

[Ninja3047]

Summary

• replace the generated pip-audit dependency group with uv audit
• stop forcing /bin/bash in generated Makefiles so recipes use Make's default POSIX shell instead of a distro-specific Bash path
• relocate namespace packages before CLI cleanup so namespace library projects remove _cli.py and __main__.py correctly
• add CI coverage for namespace library generation

Validation

• git diff --check main..HEAD
• generated a default project and verified src/python_project plus CLI modules
• generated project_namespace_import=tob.r_and_e repo_type=library and verified the namespace package exists without CLI modules
• ran generated make audit on NixOS without a SHELL= override

[ekilmer]

LGTM. Thank you!