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_connection.py

@@ -37,7 +37,9 @@ class BaseDatabaseConnection(ABC):
         pass
 
     @abstractmethod
-    def execute_query(self, sql: str, params: Optional[tuple] = None) -> List[Dict[str, Any]]:
+    def execute_query(
+        self, sql: str, params: Optional[tuple] = None
+    ) -> List[Dict[str, Any]]:
         """
         执行查询语句并返回结果