fix: auto-fix code issues (cron)

- 修复重复导入/字段
- 修复异常处理
- 修复PEP8格式问题
- 添加类型注解

backend/llm_client.py

@@ -204,15 +204,13 @@ class LLMClient:
         messages = [ChatMessage(role="user", content=prompt)]
         content = await self.chat(messages, temperature=0.1)
 
-        import re
-
         json_match = re.search(r"\{{.*?\}}", content, re.DOTALL)
         if not json_match:
             return {"intent": "unknown", "explanation": "无法解析指令"}
 
         try:
             return json.loads(json_match.group())
-        except BaseException:
+        except (json.JSONDecodeError, KeyError, TypeError):
             return {"intent": "unknown", "explanation": "解析失败"}
 
     async def analyze_entity_evolution(self, entity_name: str, mentions: list[dict]) -> str: