重构代码，统一config配置

backend/app/nodes/__init__.py

@@ -0,0 +1,19 @@
+"""
+节点模块 - 导出所有 LangGraph 节点函数
+"""
+
+from .router import should_continue
+from .llm_call import create_llm_call_node
+from .tool_call import create_tool_call_node
+from ..graph.retrieve_memory import create_retrieve_memory_node
+from .summarize import create_summarize_node
+from .finalize import finalize_node
+
+__all__ = [
+    "should_continue",
+    "create_llm_call_node",
+    "create_tool_call_node",
+    "create_retrieve_memory_node",
+    "create_summarize_node",
+    "finalize_node",
+]