refactor: 重构RAG核心组件，简化代码结构和测试文件

backend/app/core/intent_classifier.py

@@ -6,7 +6,7 @@ from typing import Optional, Dict, Any
 import sys
 import os
 
-from backend.app.model_services.chat_services import get_chat_service
+from backend.app.model_services.chat_services import get_small_llm_service
 
 
 class IntentType(Enum):
@@ -33,7 +33,7 @@ class IntentClassifier:
     """意图分类器"""
 
     def __init__(self):
-        self.llm = get_chat_service()
+        self.llm = get_small_llm_service()
         self._intent_examples = self._build_examples()
 
     def _build_examples(self) -> str: