A mobile application is more than just lines of code and attractive screens. It is a digital building  we construct for thousands, or even millions, of users. Think of it not just as a program, but as a piece of critical infrastructure: a banking service , a healthcare assistant , or a platform for managing an enterprise . What happens if the foundation of this building is weak, the elevator stops working (e.g., the payment function fails), or "leaks" appear (persistent crash