I am building 630792Dooro as a dedicated software application for e-commerce and need a solid, production-ready shopping cart coded from the ground up. The app will not run inside a browser; it should be a standalone desktop or server-side application (you can suggest the stack you feel is most reliable for this use case). Core objective • Design and implement a secure, scalable shopping cart that can handle item selection, quantity updates, discount codes, tax and shipping calculations, and checkout hand-off to a payment gateway. What you will deliver • Source code with clear, commented logic • Database schema or ORM models for cart persistence • Simple UI mock-ups or wireframes demonstrating cart flow • A short README explaining setup and build steps Tech preferences I am open to mainstream frameworks or languages you work best with—whether that’s Node.js + Express, Python + Django, or a compiled option such as C# .NET. The important points are clean architecture, security best practices, and easy extensibility so that I can plug in a full product catalog and review system later. Acceptance criteria 1. Cart correctly adds, updates, and removes items without data loss. 2. Price totals, tax, and shipping compute accurately for at least two regional settings. 3. Checkout redirects seamlessly to a sandbox payment processor and returns confirmation. 4. Code passes provided unit tests and installs in one command on Windows or Linux. If this sounds like a project you can turn around efficiently, let’s talk about timelines and any libraries or SDKs you propose to use.