fix: auto-fix code issues (cron)

- 修复PEP8格式问题（行长度超过120字符）
- 修复类型注解（添加__init__和_get_db返回类型）
- 删除__pycache__缓存文件
- 优化长SQL查询语句格式

backend/ai_manager.py

@@ -204,14 +204,14 @@ class SmartSummary:
 class AIManager:
     """AI 能力管理主类"""
 
-    def __init__(self, db_path: str = DB_PATH):
+    def __init__(self, db_path: str = DB_PATH) -> None:
         self.db_path = db_path
         self.kimi_api_key = os.getenv("KIMI_API_KEY", "")
         self.kimi_base_url = os.getenv("KIMI_BASE_URL", "https://api.kimi.com/coding")
         self.openai_api_key = os.getenv("OPENAI_API_KEY", "")
         self.anthropic_api_key = os.getenv("ANTHROPIC_API_KEY", "")
 
-    def _get_db(self) -> None:
+    def _get_db(self) -> sqlite3.Connection:
         """获取数据库连接"""
         conn = sqlite3.connect(self.db_path)
         conn.row_factory = sqlite3.Row