React + Node Developer - Onboarding Quiz Flow with Firebase Auth + Stripe

We need a developer to build a multi-step onboarding quiz as a standalone React app (Vite) that authenticates through Firebase, processes payments through Stripe, and sends data to our existing Node.js API.

The project: A 9-step onboarding flow for a subscription app. Steps include text inputs, single-select and multi-select questions, a registration screen (Firebase Auth), a plan selection screen, and a payment screen (Stripe Elements). The app deploys as static files to a subdirectory on our existing WordPress domain. No WordPress integration needed - it’s a standalone React app that lives in its own folder on the same server.

What’s already in place: Firebase project with Auth configured, a Node.js API server connected to a Postgres/MySQL database, a React Native iOS app that already talks to this API, a Stripe account, brand design and all quiz content finalized, and a detailed architecture document with file structure and data flow.

Frontend work: - Build the multi-step quiz in React (Vite, React Router) - Firebase Auth integration (email/password + Google SSO) - Stripe Elements for the payment screen - POST quiz answers to our existing Node API on completion - Responsive CSS matching our brand design from screenshots

Backend work (small scope): - Add an endpoint to receive and store quiz/onboarding answers - Add an endpoint to create Stripe payment intents - Add an endpoint to push new user data to HubSpot’s API - All endpoints added to our existing Node.js server

Must have: - React (hooks, functional components, React Router) - Node.js / Express (adding endpoints to an existing server) - Postgres or MySQL (writing queries or working with an existing ORM) - Firebase Auth (email/password + Google SSO) - Stripe Elements (@stripe/react-stripe-js) and server-side Stripe SDK - Responsive CSS (must match existing brand design from screenshots) - Experience building multi-step form flows