refactor(core): replace float('inf') with math.inf

Replace float('inf') and float('-inf') with math.inf and -math.inf from the math module for better readability and performance. Also clean up imports and remove unused speed comparison code.

No breaking changes.

docs/examples/llm_extraction_openai_pricing.py

@@ -1,10 +1,11 @@
 from crawl4ai.async_configs import LlmConfig
-from crawl4ai.extraction_strategy import *
-from crawl4ai.crawler_strategy import *
+from crawl4ai import AsyncWebCrawler, LLMExtractionStrategy
 import asyncio
+import os
+import json
 from pydantic import BaseModel, Field
 
-url = r"https://openai.com/api/pricing/"
+url = "https://openai.com/api/pricing/"
 
 
 class OpenAIModelFee(BaseModel):
@@ -14,10 +15,6 @@ class OpenAIModelFee(BaseModel):
         ..., description="Fee for output token for the OpenAI model."
     )
 
-
-from crawl4ai import AsyncWebCrawler
-
-
 async def main():
     # Use AsyncWebCrawler
     async with AsyncWebCrawler() as crawler: