Update exceptions.py

[CarlaEscobar1999]

Note

Refactors exception classes with type hints, stricter PolyApiException initialization, improved response parsing, and richer representation.

• Exceptions:
  • PolyException: add docstring and typed constructor; pass message to base Exception.
  • PolyApiException: enforce resp or error_msg presence; store typed status_code/error_msg; parse response JSON with ValueError fallback to text; construct informative base message; add detailed __repr__; remove __str__.

^{Written by Cursor Bugbot for commit a770ff1. This will update automatically on new commits. Configure here.}