Full-Stack Developer Needed: Build Backend (Supabase + OpenAI API) for Existing Next.js/React 19 App

We are launching a stealth-mode, privacy-first 21+ social application called Krypt under our parent entity, Coyah Ledger Group LLC. The entire front-end visual architecture, custom Tailwind styling, page states, Framer Motion animations, and mobile-responsive screens are 100% complete and verified. The project is built using Next.js 15+ (App Router), React 19, TypeScript, and Tailwind CSS. A live link to our interactive UI prototype is available for review, and the complete source code ZIP is ready to hand over. We are NOT looking for a front-end designer to rebuild or change the look of the application. Your sole deliverable is to build the backend engine, connect the database, implement secure API architectures, and make the application production-ready based on a strict technical specification document. Key Backend Deliverables: Live AI Chat Integration: Connect our current onboarding terminal screen to the OpenAI Assistants API (using gpt-4o-mini). The AI must ask exactly 3 sequential, culture-focused questions and evaluate the response logs to grant access.Database & Schema Architecture: Set up Supabase (PostgreSQL) tables to handle user nodes, hashed identity tokens, and event metrics with strict Row-Level Security (RLS).Data Isolation (Stripe Identity/Persona): Implement a third-party ID verification gate to verify users are 21+. Real names, exact DOBs, and ID images must never be written to the database; age must be verified via webhook, a boolean set to true, and raw identity logs instantly scrubbed. Anonymized Profiling: Implement an LLM pipeline to process the 3-question chat transcript and auto-generate an anonymous, two-part text metadata tag (e.g., "Late-Night Film Curator // Systems Architect") to serve as the user's public profile. Spatial Telemetry Shielding: Set up an event discovery database where exact street locations are kept hidden from client logs. The frontend map must only receive broad neighborhood zones and compatibility percentages, decrypting the exact coordinates via secure token only when a user is within 3 blocks of the event. Accountability Kill Switch: Build an automated system tool loop for event hosts. If an event host flags a user node for misconduct, the backend must dynamically lower their vibe credit score, invalidate active tokens, and revoke device session access if it drops below a set threshold. Required Technical Expertise: Frontend: Next.js (App Router), React 19, TypeScript, Tailwind CSS, Framer Motion. Backend/Database: Supabase (PostgreSQL), Next.js Server Actions / API Routes.AI/APIs: OpenAI Assistants API (thread token management), Stripe Identity SDK, or Persona SDK.Security: Cryptographic device fingerprinting, WebAuthn Passkeys (NextAuth/Auth.js preferred).Contract & Budget Terms: This is a Fixed-Price Contract funded entirely out-of-pocket by a solo founder. The budget is $1,500, strictly managed through three sequential milestone payments in Upwork Escrow. We will not convert this to an hourly project. How to Apply: Please respond with specific examples of full-stack projects you have personally engineered involving Supabase data structures and OpenAI streaming integrations. Do not send generic design portfolios. Please include the word "KRYPT_CORE" at the top of your proposal so we know you read this full technical scope.