Refactor test files for improved readability and consistency

- Removed unnecessary blank lines and adjusted formatting in test files.
- Ensured consistent use of commas in function calls and assertions across various test cases.
- Updated import statements for better organization and clarity.
- Enhanced mock setups in tests for better isolation and reliability.
- Improved assertions to follow a consistent style for better readability.

app/schemas/__init__.py

@@ -39,7 +39,7 @@ __all__ = [
     "UserResponse",
     # Common schemas
     "HealthResponse",
-    "MessageResponse", 
+    "MessageResponse",
     "StatusResponse",
     # Player schemas
     "PlayerModeRequest",