I need an e-commerce app built at an affordable price. The app will have around 20 products initially. App should have all the functionality of an e-commerce app like customer login/signup, cart, checkout, otp verification, payment methods, wishlist, my account , admin panel to add/remove products etc. Please quote your most competitive price. Also reply if you have a proposal document for app development that I can go through. Also include in your reply the platforms (ios and Android) that you'll provide the app for.