Can I vibe code Smartrr?

Build a custom Shopify Subscription Management backend and Portal App using Node.js, Express, and modern Shopify Admin GraphQL APIs.

1. DATA MODEL & SHOPIFY INTEGRATION
- Store Subscription Contracts linked to Shopify customer IDs and Selling Plan IDs.
- Track contract status (ACTIVE, PAUSED, CANCELLED), next billing date, delivery frequency, line items, and vaulting payment paymentMethodId.
- Store billing attempt histories and failure counts.

2. CORE FUNCTIONALITY
- Webhook Listener: Process subscriptionContract/create, subscriptionContract/update, and subscriptionBillingAttempt/failure events from Shopify.
- Customer Portal API: Provide authenticated endpoints for end-users to: (a) Skip next renewal, (b) Pause/Resume subscription, (c) Swap line item product variant IDs, (d) Change delivery frequency, (e) Update shipping address.
- Storefront Widget: Render selling plan options on the product page via Theme App Extension using App Proxies for security.
- Dunning Engine: On payment failure, trigger an exponential backoff schedule (1 day, 3 days, 7 days) calling `subscriptionBillingAttemptCreate` mutation up to 3 times before setting contract to EXPIRED.

3. INTEGRATION EVENTS
- Send Webhook payloads to Klaviyo upon events: 'Subscription Created', 'Subscription Billing Failed', 'Subscription Cancelled', and 'Upcoming Renewal (3 Days)' for email triggers.

4. FAILURE MODES & OUT OF SCOPE
- Handle Shopify GraphQL API rate limits (bucket cost) during batch renewal runs by queuing jobs with BullMQ and Redis.
- Ensure concurrent updates to a contract (e.g. customer swapping product during an active billing attempt) throw an atomic lock error.
- Out of Scope: Direct credit card card processing (rely entirely on Shopify's vaulted payment tokens and native checkout).

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