Implement IronLicensing Python SDK

- LicenseClient for validation and activation
- Feature checking with has_feature/require_feature
- Trial management
- Purchase/checkout flow
- Offline caching with grace period
- License change callbacks
- Full async support with httpx
- Comprehensive README

.gitignore

@@ -0,0 +1,36 @@
+# Byte-compiled / optimized / DLL files
+__pycache__/
+*.py[cod]
+*$py.class
+
+# Distribution / packaging
+dist/
+build/
+*.egg-info/
+*.egg
+
+# Virtual environments
+.venv/
+venv/
+ENV/
+
+# IDE
+.idea/
+.vscode/
+*.swp
+*.swo
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Testing
+.pytest_cache/
+.coverage
+htmlcov/
+
+# Type checking
+.mypy_cache/
+
+# Local storage
+.ironlicensing/