Can I vibe code Selleasy?

Create a custom Shopify app and Theme App Extension to replicate core Selleasy functionality for upsells and cross-sells. 1. DATA MODEL: Define Shopify Product Metafields for 'upsell_handles' (list of product handles) and 'upsell_discount_percent' (number). 2. FRONTEND WIDGET: Build a vanilla JS / Web Component theme app extension embedded on product pages and inside the Ajax cart drawer. The widget fetches the target product metafields via the Shopify Storefront API. Display recommended items with a '1-Click Add to Cart' button that uses the Shopify AJAX Cart API (/cart/add.js) to append items without page reloads. 3. POST-PURCHASE EXTENSION: Build a Shopify App Extension using the Post-Purchase UI Extension API. After payment submission, intercept the thank-you page transition, display a single-item discounted offer page, and if accepted, call the `calculateChanges` and `acceptOffer` API mutations to update the existing order. 4. FAILURE MODES & EDGE CASES: If an offered upsell product is out of stock, automatically hide the offer widget. Ensure multi-currency formatting relies on Shopify's native currency selector object. Prevent double-submitting items by disabling UI buttons during active fetch calls. OUT OF SCOPE: Complex machine-learning recommendation algorithms; simple manual metafield mappings and tag-based rules are sufficient.

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