Every frontend developer has experienced this sequence: You start building an interactive web application. The backend is not yet ready, so you connect to a popular free mock API like JSONPlaceholder or a local static db.json file. You fetch data with a GET request. The cards render nicely on screen. You build a form to create a new user or submit an order. You send a POST request. The API responds with a cheerful { id: 101, status: "created" } . You trigger your UI's refresh...