feat: cleanup unused code and enhance documentation for v0.7.1

- Remove unused StealthConfig from browser_manager.py
- Update LinkPreviewConfig import path in __init__.py and examples
- Fix infinity handling in content_scraping_strategy.py (use 0 instead of float('inf'))
- Remove sanitize_json_data functions from API endpoints
- Add comprehensive C4A Script documentation to release notes
- Update v0.7.0 release notes with improved code examples
- Create v0.7.1 release notes focusing on cleanup and documentation improvements
- Update demo files with corrected import paths and examples
- Fix virtual scroll and adaptive crawling examples across documentation

🤖 Generated with Claude Code

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

tests/test_link_extractor.py

@@ -5,7 +5,7 @@ Test script for Link Extractor functionality
 
 from crawl4ai.models import Link
 from crawl4ai import AsyncWebCrawler, CrawlerRunConfig
-from crawl4ai.async_configs import LinkPreviewConfig
+from crawl4ai import LinkPreviewConfig
 import asyncio
 import sys
 import os
@@ -237,7 +237,7 @@ def test_config_examples():
             print(f"     {key}: {value}")
 
         print("   Usage:")
-        print("     from crawl4ai.async_configs import LinkPreviewConfig")
+        print("     from crawl4ai import LinkPreviewConfig")
         print("     config = CrawlerRunConfig(")
         print("         link_preview_config=LinkPreviewConfig(")
         for key, value in config_dict.items():