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.

main.py

@@ -17,6 +17,7 @@ from routes.currencies import router as currencies_router
 from routes.simulations import router as simulations_router
 from routes.maintenance import router as maintenance_router
 from routes.settings import router as settings_router
+from routes.users import router as users_router
 
 # Initialize database schema
 Base.metadata.create_all(bind=engine)
@@ -30,6 +31,7 @@ async def json_validation(
 ) -> Response:
     return await validate_json(request, call_next)
 
+
 app.mount("/static", StaticFiles(directory="static"), name="static")
 
 # Include API routers
@@ -46,3 +48,4 @@ app.include_router(reporting_router)
 app.include_router(currencies_router)
 app.include_router(settings_router)
 app.include_router(ui_router)
+app.include_router(users_router)