Add pip installation support via pyproject.toml

[Copilot]

Buzzard had no packaging metadata, making it impossible to install via pip — users had to run python buzzard.py directly from the repo root.

Changes

• pyproject.toml — standard PEP 517/518 packaging config with project metadata, minimum-version-pinned runtime dependencies, an edelweiss optional extra for the EdelweissFE interface, and a buzzard console script entry point
• buzzard/__main__.py — extracts CLI logic from buzzard.py into a proper main() function; enables both buzzard (console script) and python -m buzzard
• buzzard.py — reduced to a thin shim that delegates to buzzard.__main__:main for backward compatibility
• .gitignore — adds *.egg-info

Usage after install

pip install .          # or: pip install -e .
buzzard config.py      # console script on PATH
python -m buzzard config.py  # also works

The EdelweissFE interface dependency is opt-in:

pip install ".[edelweiss]"