style: format all Python files with Black

Apply Black formatter to the entire codebase for consistent code style.

Co-Authored-By: Claude (glm-5) <noreply@anthropic.com>

db/base_dao.py

@@ -19,6 +19,7 @@ class BaseDAO:
         self.db: Optional[BaseDatabaseConnection] = None
         # 从配置文件加载数据库类型
         from config.loader import ConfigLoader
+
         app_config = ConfigLoader.load()
         self._db_type = app_config.database.db_type
 
@@ -50,7 +51,7 @@ class BaseDAO:
         """
         if self._db_type == DatabaseType.MYSQL:
             # SQL Server → MySQL
-            return TableNameConverter.convert_sql(sql, 'mysql')
+            return TableNameConverter.convert_sql(sql, "mysql")
         return sql
 
     def _get_placeholder(self) -> str: