Fixes#1273
- Replace deprecated stealth_async import with Stealth class
- Add stealth flag to BrowserConfig (default: true)
- Update async_crawler_strategy to use Stealth().apply_stealth_async()
- Remove obsolete StealthConfig from browser_manager
- Maintain backward compatibility with existing stealth functionality
This fixes compatibility issues with playwright-stealth v2.0.0+ where the API changed from stealth_async function to Stealth class.
test: Add comprehensive tests for playwright-stealth v2.0.0+ compatibility
- Test Stealth class import and instantiation
- Test apply_stealth_async method availability
- Test BrowserConfig stealth flag functionality
- Test stealth flag serialization
- Verify backward compatibility with existing stealth functionality
