only use langchain if env vars are set

src/main.py

@@ -15,12 +15,14 @@ from tools.base_tool import ToolContext, set_tool_context
 
 load_dotenv()
 
+
 logging.basicConfig(
     level=logging.INFO,
     format='%(asctime)s - %(name)s - %(levelname)s - %(message)s'
 )
 logging.getLogger('watchfiles').setLevel(logging.WARNING)
 
+if all(var in os.environ for var in ['LANGFUSE_PUBLIC_KEY', 'LANGFUSE_SECRET_KEY', 'LANGFUSE_HOST']):
     langfuse = get_client()
 
     if langfuse.auth_check():