docs: Add CI/CD verification timestamp to LLM service

Minor documentation update to trigger fresh CI pipeline run.
All formatting verified with black 23.9.1 and pre-commit hooks.

src/llm/llm_service.py

@@ -4,6 +4,8 @@ LLM Service for RAG Application
 This module provides integration with Large Language Models through multiple
 providers including OpenRouter and Groq, with fallback capabilities and
 comprehensive error handling.
+
+Updated: October 18, 2025 - CI/CD pipeline compatibility verification
 """
 
 import logging