feat: add stealth mode and enhance undetected browser support

- Add playwright-stealth integration with enable_stealth parameter in BrowserConfig
- Merge undetected browser strategy into main async_crawler_strategy.py using adapter pattern
- Add browser adapters (BrowserAdapter, PlaywrightAdapter, UndetectedAdapter) for flexible browser switching
- Update install.py to install both playwright and patchright browsers automatically
- Add comprehensive documentation for anti-bot features (stealth mode + undetected browser)
- Create examples demonstrating stealth mode usage and comparison tests
- Update pyproject.toml and requirements.txt with patchright>=1.49.0 and other dependencies
- Remove duplicate/unused dependencies (alphashape, cssselect, pyperclip, shapely, selenium)
- Add dependency checker tool in tests/check_dependencies.py

Breaking changes: None - all existing functionality preserved

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

crawl4ai/__init__.py

@@ -88,6 +88,13 @@ from .script import (
     ErrorDetail
 )
 
+# Browser Adapters
+from .browser_adapter import (
+    BrowserAdapter,
+    PlaywrightAdapter,
+    UndetectedAdapter
+)
+
 from .utils import (
     start_colab_display_server,
     setup_colab_environment
@@ -173,6 +180,10 @@ __all__ = [
     "CompilationResult",
     "ValidationResult",
     "ErrorDetail",
+    # Browser Adapters
+    "BrowserAdapter",
+    "PlaywrightAdapter", 
+    "UndetectedAdapter",
 ]