Full-Stack Developer for Premium B2B Sourcing Ecosystem (Custom SaaS)

I am the CEO of a Top-Rated US-based Global Product Sourcing Agency. I am looking for an elite, independent full-stack developer to build a complete custom B2B sourcing ecosystem from scratch. I am currently traveling on business and do not have time to micromanage you. I expect you to act as a technical consultant. I will give you the business goals, and you will present me with the best architecture and design options for me to approve. (Agencies will be ignored. Independent freelancers only). Ecosystem Requirements: 1. Client Portal: B2B buyers log in, view custom quotes, approve orders, and track shipping. 2. Admin Dashboard: A backend for me to manage clients, input custom quotes across various industries (construction, electronics, etc.), and track orders. 3. Custom Payments: I require embedded custom payments (Stripe Elements). Buyers must pay seamlessly inside my portal without being redirected to a generic Stripe checkout page. 4. Complex Logic: RFQ (Request for Quote) form routing and automated status updates. 5. Premium Design: The UI/UX must look like a multi-million-dollar Silicon Valley SaaS product. I do not want cheap, tacky, or lazy AI-generated designs. To Apply, you MUST include: 1. Exactly 2 links to the most complex, premium custom web apps/dashboards you have personally built. 2. Undeniable proof that you built them (e.g., a screen-recording or screenshot showing you logged into the backend codebase or admin panel). If you submit a stolen portfolio without proof, you will be rejected. 3. Tell me exactly which tech stack you recommend we use to build this (e.g., React, Next.js, Laravel) and explain WHY it is the best option.