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.

tests/hub/test_simple.py

@@ -0,0 +1,30 @@
+# test.py
+from crawl4ai import CrawlerHub
+import json
+
+async def amazon_example():
+    if (crawler_cls := CrawlerHub.get("amazon_product")) :
+        crawler = crawler_cls()
+        print(f"Crawler version: {crawler_cls.meta['version']}")
+        print(f"Rate limits: {crawler_cls.meta.get('rate_limit', 'Unlimited')}")
+        print(await crawler.run("https://amazon.com/test"))
+    else:
+        print("Crawler not found!")
+
+async def google_example():
+    # Get crawler dynamically
+    crawler_cls = CrawlerHub.get("google_search")
+    crawler = crawler_cls()
+
+    # Text search
+    text_results = await crawler.run(query="apple inc", search_type="text",  schema_cache_path="/Users/unclecode/.crawl4ai")
+    print(json.loads(text_results))
+
+    # Image search
+    image_results = await crawler.run(query="apple inc", search_type="image")
+    print(image_results)
+
+if __name__ == "__main__":
+    import asyncio
+    # asyncio.run(amazon_example())
+    asyncio.run(google_example())