Refactor test cases for improved readability and consistency

- Updated test functions in various test files to enhance code clarity by formatting long lines and improving indentation.
- Adjusted assertions to use multi-line formatting for better readability.
- Added new test cases for theme settings API to ensure proper functionality.
- Ensured consistent use of line breaks and spacing across test files for uniformity.

middleware/validation.py

@@ -4,7 +4,10 @@ from fastapi import HTTPException, Request, Response
 
 MiddlewareCallNext = Callable[[Request], Awaitable[Response]]
 
-async def validate_json(request: Request, call_next: MiddlewareCallNext) -> Response:
+
+async def validate_json(
+    request: Request, call_next: MiddlewareCallNext
+) -> Response:
     # Only validate JSON for requests with a body
     if request.method in ("POST", "PUT", "PATCH"):
         try: