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>

docs/examples/undetectability/undetected_basic_test.py

@@ -0,0 +1,74 @@
+"""
+Basic Undetected Browser Test
+Simple example to test if undetected mode works
+"""
+
+import asyncio
+from crawl4ai import AsyncWebCrawler, BrowserConfig
+
+async def test_regular_mode():
+    """Test with regular browser"""
+    print("Testing Regular Browser Mode...")
+    browser_config = BrowserConfig(
+        headless=False,
+        verbose=True
+    )
+    
+    async with AsyncWebCrawler(config=browser_config) as crawler:
+        result = await crawler.arun(url="https://www.example.com")
+        print(f"Regular Mode - Success: {result.success}")
+        print(f"Regular Mode - Status: {result.status_code}")
+        print(f"Regular Mode - Content length: {len(result.markdown.raw_markdown)}")
+        print(f"Regular Mode - First 100 chars: {result.markdown.raw_markdown[:100]}...")
+        return result.success
+
+async def test_undetected_mode():
+    """Test with undetected browser"""
+    print("\nTesting Undetected Browser Mode...")
+    from crawl4ai import UndetectedAdapter
+    from crawl4ai.async_crawler_strategy import AsyncPlaywrightCrawlerStrategy
+    
+    browser_config = BrowserConfig(
+        headless=False,
+        verbose=True
+    )
+    
+    # Create undetected adapter
+    undetected_adapter = UndetectedAdapter()
+    
+    # Create strategy with undetected adapter
+    crawler_strategy = AsyncPlaywrightCrawlerStrategy(
+        browser_config=browser_config,
+        browser_adapter=undetected_adapter
+    )
+    
+    async with AsyncWebCrawler(
+        crawler_strategy=crawler_strategy,
+        config=browser_config
+    ) as crawler:
+        result = await crawler.arun(url="https://www.example.com")
+        print(f"Undetected Mode - Success: {result.success}")
+        print(f"Undetected Mode - Status: {result.status_code}")
+        print(f"Undetected Mode - Content length: {len(result.markdown.raw_markdown)}")
+        print(f"Undetected Mode - First 100 chars: {result.markdown.raw_markdown[:100]}...")
+        return result.success
+
+async def main():
+    """Run both tests"""
+    print("🤖 Crawl4AI Basic Adapter Test\n")
+    
+    # Test regular mode
+    regular_success = await test_regular_mode()
+    
+    # Test undetected mode
+    undetected_success = await test_undetected_mode()
+    
+    # Summary
+    print("\n" + "="*50)
+    print("Summary:")
+    print(f"Regular Mode: {'✅ Success' if regular_success else '❌ Failed'}")
+    print(f"Undetected Mode: {'✅ Success' if undetected_success else '❌ Failed'}")
+    print("="*50)
+
+if __name__ == "__main__":
+    asyncio.run(main())