feat(logger): add abstract logger base class and file logger implementation

Add AsyncLoggerBase abstract class to standardize logger interface and introduce AsyncFileLogger for file-only logging. Remove deprecated always_bypass_cache parameter and clean up AsyncWebCrawler initialization.

BREAKING CHANGE: Removed deprecated 'always_by_pass_cache' parameter. Use BrowserConfig cache settings instead.

docs/examples/hello_world.py

@@ -1,5 +1,12 @@
 import asyncio
-from crawl4ai import *
+from crawl4ai import (
+    AsyncWebCrawler,
+    BrowserConfig,
+    CrawlerRunConfig,
+    CacheMode,
+    DefaultMarkdownGenerator,
+    PruningContentFilter,
+)
 
 
 async def main():