Add optional C++ and Python integrity verification

[romelespana07-create]

Summary

Adds optional integrity verification for both anti-cheat implementations.

Changes

• Keeps the C++ executable CRC32 guard optional via JAVELIN_EXPECTED_CRC32
• Fixes the invalid 0xCRC exit code so the C++ file compiles
• Adds a Python SHA-256 script integrity guard using JAVELIN_EXPECTED_SHA256
• Documents how to set both expected values
• Adds Python tests for disabled, matching, and mismatching integrity checks

Tests

python -m unittest test_integrity.py
python -m py_compile AntiCheat.py test_integrity.py

Fixes #4.

[romelespana07-create]

Hi! Checking in on this bounty submission. The PR is mergeable and includes optional C++ CRC32 executable integrity, Python SHA-256 script integrity via JAVELIN_EXPECTED_SHA256, docs, and tests. Happy to make any requested adjustments.

[romelespana07-create]

Follow-up on June 12: this PR remains ready for review. It adds optional C++ and Python integrity verification with tests and README updates. Please let me know if any changes are needed for bounty evaluation.