Function get_python_package_version

pub fn get_python_package_version(package_name: &str) -> String

Attempt to retrieve the __version__ attribute of a Python package.

When the requested package cannot be imported, or when it does not define a __version__ attribute, the function returns a human-readable fallback string that starts with "Unavailable" so that downstream code can distinguish real version strings from error cases.

This helper is primarily intended for diagnostic/logging purposes inside the PoseiTrader Python bindings.