Python 3 port + tests + CI/CD + contribution docs

[aman179102]

Summary

Complete modernization of Cloakify: Python 3 port, comprehensive test suite, CI/CD pipelines, and contribution documentation.

Changes

Python 3 Port

• Converted all print statements to print() function calls
• Replaced deprecated base64.encodestring with base64.encodebytes
• Fixed exit calls to sys.exit(1)
• Added proper Python 3 shebangs
• All scripts now run on Python 3.8+ (tested up to 3.12)

Testing (16 tests, all passing)

• Core roundtrip tests (cloak → decloak returns original)
• Binary payload support (all 256 byte values)
• Unicode cipher support
• Large payload testing (10KB)
• Different cipher → different output verification
• Edge cases (nonexistent files, invalid content, empty payloads)
• Output validation (cloaked content only contains cipher words)

CI/CD

• ci.yml: Automated testing on Python 3.8-3.12 with coverage
• release.yml: PyPI publishing workflow

Documentation

• CONTRIBUTING.md with setup and testing guide
• CODE_OF_CONDUCT.md
• SECURITY.md with vulnerability disclosure policy
• PR template with checklist

Dev Tooling

• pyproject.toml with pytest, black, isort, mypy configuration
• pre-commit hooks (trailing-whitespace, end-of-file-fixer, black, isort)
• .coveragerc with 80% coverage target
• .gitignore for Python project

Verification