refactor(core): reorganize project structure and remove legacy code

Major reorganization of the project structure:
- Moved legacy synchronous crawler code to legacy folder
- Removed deprecated CLI and docs manager
- Consolidated version manager into utils.py
- Added CrawlerHub to __init__.py exports
- Fixed type hints in async_webcrawler.py
- Fixed minor bugs in chunking and crawler strategies

BREAKING CHANGE: Removed synchronous WebCrawler, CLI, and docs management functionality. Users should migrate to AsyncWebCrawler.

crawl4ai/async_crawler_strategy.py

@@ -1265,6 +1265,7 @@ class AsyncPlaywrightCrawlerStrategy(AsyncCrawlerStrategy):
         """
         config.url = url
         response_headers = {}
+        execution_result = None
         status_code = None
         redirected_url = url 
 
@@ -1522,6 +1523,7 @@ class AsyncPlaywrightCrawlerStrategy(AsyncCrawlerStrategy):
                 execution_result = await self.robust_execute_user_script(
                     page, config.js_code
                 )
+
                 if not execution_result["success"]:
                     self.logger.warning(
                         message="User script execution had issues: {error}",