fixed Boost::system include for Boost >= 1.89

[hshose]

Issue:
From Boost 1.89 on, the Boost::system library doesn't exist anymore.

Proposed fix:
Replace Boost::system with Boost::boost.

Tested with boost 1.89, python 14.

[whoenig]

Thanks! The CI seems to be broken (again:-/), so it's difficult for me to check if your contribution will break older version (such as boost 1.83 that is still used on Ubuntu), before fixing these issues. Conceptually it makes sense, though and your fix might address the issues the CI finds on Mac OS (not sure what's going on for Windows and Linux, yet).

[hshose]

rebased to current head; attempted vibe-fixing linux and windows CI errors. MacOS CI error on main is likely fixed by the boost fixes.