refactor(deep-crawling): reorganize deep crawling strategies and add new implementations

Split deep crawling code into separate strategy files for better organization and maintainability. Added new BFF (Best First) and DFS crawling strategies. Introduced base strategy class and common types.

BREAKING CHANGE: Deep crawling implementation has been split into multiple files. Import paths for deep crawling strategies have changed.

crawl4ai/deep_crawling/bfs_strategy.py

@@ -5,15 +5,11 @@ from datetime import datetime
 from typing import AsyncGenerator, Optional, Set, Dict, List, Tuple
 from urllib.parse import urlparse
 
-from ..models import CrawlResult, TraversalStats
+from ..models import TraversalStats
 from .filters import FastFilterChain
 from .scorers import FastURLScorer
-
-from typing import TYPE_CHECKING
 from . import DeepCrawlStrategy  
-if TYPE_CHECKING:
-    from ..async_configs import CrawlerRunConfig
-    from ..async_webcrawler import AsyncWebCrawler
+from ..types import AsyncWebCrawler, CrawlerRunConfig, CrawlResult
 
 class BFSDeepCrawlStrategy(DeepCrawlStrategy):
     """
@@ -107,8 +103,8 @@ class BFSDeepCrawlStrategy(DeepCrawlStrategy):
     async def _arun_batch(
         self,
         start_url: str,
-        crawler: "AsyncWebCrawler",
-        config: "CrawlerRunConfig",
+        crawler: AsyncWebCrawler,
+        config: CrawlerRunConfig,
     ) -> List[CrawlResult]:
         """
         Batch (non-streaming) mode:
@@ -148,8 +144,8 @@ class BFSDeepCrawlStrategy(DeepCrawlStrategy):
     async def _arun_stream(
         self,
         start_url: str,
-        crawler: "AsyncWebCrawler",
-        config: "CrawlerRunConfig",
+        crawler: AsyncWebCrawler,
+        config: CrawlerRunConfig,
     ) -> AsyncGenerator[CrawlResult, None]:
         """
         Streaming mode: