Can I vibe code Cartpanda?

Build a self-hosted LATAM-focused single-page checkout engine using Next.js 14 (App Router), Node.js (Fastify), PostgreSQL, and Redis.

1. DATA MODEL:
Create database models for:
- Merchant (id, api_keys, gateway_credentials)
- CheckoutSession (id, cart_items, customer_info, status: pending/paid/expired, payment_method)
- OrderBump (id, product_id, price, title, active)
- UpsellOffer (id, trigger_product_id, offer_product_id, price, position)
- PaymentTransaction (id, checkout_session_id, gateway, payload, status, pix_qr_code, pix_copia_e_cola)

2. CORE FUNCTIONALITY:
- Single-page frontend checkout displaying cart items, customer address fields (CPF/CNPJ field for Brazil), line-item summary, and interactive checkable Order Bumps.
- Direct payment integration endpoints for Mercado Pago and Stripe (Credit Card, PIX, Boleto).
- Real-time PIX payment screen displaying copy-paste key and dynamic QR code with a 10-minute countdown timer. Implement a WebSocket connection or polling mechanism to detect instant PIX payment completion.
- Post-Purchase Upsell Engine: Upon successful primary payment authorization, render a post-purchase offer page BEFORE the final thank-you screen. Use the stored payment token to execute a 1-click purchase if accepted.

3. INTEGRATION & WEBHOOK HANDLER:
- Implement idempotent webhook processing endpoints for payment gateways using Redis for locks to prevent duplicate order generation.
- Send outbound order payload to Shopify Admin API or custom webhook receiver upon successful payment confirmation.

4. FAILURE MODES & RESILIENCE:
- If a post-purchase 1-click upsell charge fails, capture the primary order, log the upsell failure, and proceed to thank-you page without cancelling the original transaction.
- Handle PIX expiration gracefully by updating state to expired and prompting the customer to regenerate a code.

5. OUT OF SCOPE:
- Native inventory warehousing logic, full storefront browsing pages, customer account management, multi-vendor marketplace split payouts.

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