The NgrokServiceTests were failing in CI with "cannot find 'TestError' in scope"
because TestError.skip was being used but the skip case was not defined.
- Add TestError.skip(String) case to TestFixtures
- Update NgrokServiceTests to use TestFixtures.TestError.skip for proper namespacing
- Move all macOS-specific code from root to mac/ directory
- Move app icons and assets to dedicated assets/ directory
- Update GitHub workflows for new structure
- Consolidate documentation files
- Clean up root directory for better multi-platform organization
