dongshuai921/promall ? reverse-engineered prompt

Build me a clean Vue app called Promall that feels like a simple shopping or promo site. I want a polished homepage with a clear header, some featured content cards, a few sections for products or promotions, and a footer, all laid out nicely on desktop and mobile. Make it look modern and easy to use, with smooth navigation and placeholder data that I can replace later.

Set it up so I can run it locally, make changes easily, and build it for production without errors. If you need to, look up the current Vue docs online for anything that helps you finish it cleanly. Keep the code organized and readable, and make the design feel like a real small ecommerce landing page rather than a generic demo.