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.

tests/loggers/test_logger.py

@@ -0,0 +1,80 @@
+import asyncio
+from crawl4ai import AsyncWebCrawler, BrowserConfig, CrawlerRunConfig, CacheMode, AsyncLoggerBase
+import os
+from datetime import datetime
+
+class AsyncFileLogger(AsyncLoggerBase):
+    """
+    File-only asynchronous logger that writes logs to a specified file.
+    """
+
+    def __init__(self, log_file: str):
+        """
+        Initialize the file logger.
+
+        Args:
+            log_file: File path for logging
+        """
+        self.log_file = log_file
+        os.makedirs(os.path.dirname(os.path.abspath(log_file)), exist_ok=True)
+
+    def _write_to_file(self, level: str, message: str, tag: str):
+        """Write a message to the log file."""
+        timestamp = datetime.now().strftime("%Y-%m-%d %H:%M:%S.%f")[:-3]
+        with open(self.log_file, "a", encoding="utf-8") as f:
+            f.write(f"[{timestamp}] [{level}] [{tag}] {message}\n")
+
+    def debug(self, message: str, tag: str = "DEBUG", **kwargs):
+        """Log a debug message to file."""
+        self._write_to_file("DEBUG", message, tag)
+
+    def info(self, message: str, tag: str = "INFO", **kwargs):
+        """Log an info message to file."""
+        self._write_to_file("INFO", message, tag)
+
+    def success(self, message: str, tag: str = "SUCCESS", **kwargs):
+        """Log a success message to file."""
+        self._write_to_file("SUCCESS", message, tag)
+
+    def warning(self, message: str, tag: str = "WARNING", **kwargs):
+        """Log a warning message to file."""
+        self._write_to_file("WARNING", message, tag)
+
+    def error(self, message: str, tag: str = "ERROR", **kwargs):
+        """Log an error message to file."""
+        self._write_to_file("ERROR", message, tag)
+
+    def url_status(self, url: str, success: bool, timing: float, tag: str = "FETCH", url_length: int = 50):
+        """Log URL fetch status to file."""
+        status = "SUCCESS" if success else "FAILED"
+        message = f"{url[:url_length]}... | Status: {status} | Time: {timing:.2f}s"
+        self._write_to_file("URL_STATUS", message, tag)
+
+    def error_status(self, url: str, error: str, tag: str = "ERROR", url_length: int = 50):
+        """Log error status to file."""
+        message = f"{url[:url_length]}... | Error: {error}"
+        self._write_to_file("ERROR", message, tag)
+
+async def main():
+    browser_config = BrowserConfig(headless=True, verbose=True)
+    crawler = AsyncWebCrawler(config=browser_config, logger=AsyncFileLogger("/Users/unclecode/devs/crawl4ai/.private/tmp/crawl.log"))
+    await crawler.start()
+    
+    try:
+        crawl_config = CrawlerRunConfig(
+            cache_mode=CacheMode.BYPASS,
+        )
+        # Use the crawler multiple times
+        result = await crawler.arun(
+            url='https://kidocode.com/',
+            config=crawl_config
+        )
+        if result.success:
+            print("First crawl - Raw Markdown Length:", len(result.markdown_v2.raw_markdown))
+            
+    finally:
+        # Always ensure we close the crawler
+        await crawler.close()
+
+if __name__ == "__main__":
+    asyncio.run(main())