[ARITH] Expose allow_override parameter in Python Analyzer.bind()

[fpedd]

The C++ Analyzer::Bind() already supports allow_override, but the FFI bridge always used the default (false). This change threads the optional argument through the FFI layer and the Python wrapper so callers can rebind variables without triggering an error.

[gemini-code-assist]

Code Review

This pull request introduces an optional allow_override parameter to the Analyzer.bind method, allowing users to update existing variable bindings. The changes include updates to the Python API, the C++ FFI layer, and the addition of a unit test to verify the new functionality. A review comment suggests removing an unnecessary return statement in the Python implementation to align with the method's None return type hint.