Finish & launch-harden a Next.js + Supabase + Stripe prediction-game PWA

Overview I'm completing a World Cup football-prediction game (PWA) and need a senior full-stack engineer to take it from "mostly built" to "tested and launchable." The architecture and most screens exist; this is finishing, wiring, polishing, and hardening — not a greenfield build. Stack: Next.js (App Router) · React · Redux Toolkit · Supabase (Postgres, RLS) · next-auth v5 · Stripe · Vercel · PWA. Scope / Deliverables (fixed-price, by milestone): Auth & onboarding — signup, email verification, avatar selection, league join, working end-to-end on staging. Gameplay — bet placement (Home/Draw/Away), game interactions, coin economy. Settlement engine — match resolution → parimutuel payout → leaderboard/ranking updates, verified correct. Design implementation — adjust the UI to match provided HTML mockups + design tokens. Admin tooling — entering match results and resolving matches (usable by a non-developer). Transactional email — verification / reset / receipts working. Payments (Stripe test mode) — paid-league checkout + webhook end-to-end (can be a later milestone). Security hardening — complete a private checklist (RLS, rate-limiting, headers, auth). Bug-fix & cleanup pass, delivered as reviewable PRs against a clean branch. What I provide: sandboxed GitHub access, HTML mockups + tokens, a written scope/Definition-of-Done with per-item acceptance criteria, a seeded dev Supabase project, and Stripe test keys. You will not receive production credentials or real user data — all work is on staging, delivered via pull requests. Required: demonstrable Next.js App Router + Supabase + Stripe experience; comfort with Postgres/RLS and auth flows. Screening questions: Link a Next.js + Supabase project you shipped (Stripe a plus). How would you verify a parimutuel payout/settlement is correct? Rough estimate + milestone breakdown for the scope above