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/ai_manager.py

@@ -209,7 +209,7 @@ class AIManager:
         self.openai_api_key = os.getenv("OPENAI_API_KEY", "")
         self.anthropic_api_key = os.getenv("ANTHROPIC_API_KEY", "")
 
-    def _get_db(self):
+    def _get_db(self) -> None:
         """获取数据库连接"""
         conn = sqlite3.connect(self.db_path)
         conn.row_factory = sqlite3.Row
@@ -921,7 +921,6 @@ class AIManager:
 
         # 解析关键要点
         key_points = []
-        import re
 
         # 尝试从 JSON 中提取
         json_match = re.search(r"\{.*?\}", content, re.DOTALL)
@@ -1312,7 +1311,7 @@ class AIManager:
 
             return [self._row_to_prediction_result(row) for row in rows]
 
-    def update_prediction_feedback(self, prediction_id: str, actual_value: str, is_correct: bool):
+    def update_prediction_feedback(self, prediction_id: str, actual_value: str, is_correct: bool) -> None:
         """更新预测反馈（用于模型改进）"""
         with self._get_db() as conn:
             conn.execute(