Can I vibe code LoyaltyLion?

Build a headless loyalty and referral engine microservice for Shopify using Node.js, Fastify, PostgreSQL, and Prisma.

CORE DATA MODEL:
1. Customer: shopify_customer_id (unique bigint), email, points_balance (integer), lifetime_points (integer), current_tier_id (FK), referral_code (unique string).
2. PointTransaction: id, customer_id, points (positive or negative), reason (purchase, referral, review, redemption, refund), reference_id (e.g., Shopify order_id), created_at.
3. VIP_Tier: id, name, minimum_spend (cents), points_multiplier (decimal), perks_json.
4. Reward: id, name, points_cost, discount_type (fixed_amount, percentage, free_shipping), discount_value, shopify_price_rule_id.
5. Referral: id, referrer_customer_id, referred_customer_id, status (pending, completed), shopify_order_id.

REQUIRED INTEGRATIONS & API ENDPOINTS:
1. Webhook Handler (`POST /webhooks/shopify/orders-create`):
   - Authenticate HMAC signature from Shopify.
   - Calculate earned points: `(order.total_price - shipping - tax) * active_tier_multiplier`.
   - Idempotency check: Ignore if `order_id` already exists in PointTransaction.
   - Process referrals: If order contains a referral discount code, credit the referrer with bonus points once order is paid.
2. Webhook Handler (`POST /webhooks/shopify/orders-cancelled`):
   - Deduct points earned from the cancelled order. Handle edge case where customer already redeemed points (allow negative points_balance or cap at 0).
3. Public Storefront Widget API (`GET /api/v1/customer/loyalty-summary`):
   - Expects authenticated Shopify App Proxy headers or JWT.
   - Returns points_balance, current_tier, progress_to_next_tier, available_rewards, and unique referral_url.
4. Reward Redemption API (`POST /api/v1/rewards/redeem`):
   - Atomic transaction: Deduct points from balance.
   - Call Shopify Admin REST/GraphQL API to generate a unique single-use Discount Code via Price Rules.
   - Return discount code string to frontend widget.
5. Klaviyo Sync Worker:
   - On point balance change or tier upgrade, asynchronously emit event to Klaviyo REST API (`/api/events`) updating profile attributes (`loyalty_points`, `vip_tier`, `referral_link`).

OUT OF SCOPE:
- Custom drag-and-drop widget builder UI.
- Native mobile app SDKs.
- POS hardware integrations.

FAILURE MODES TO HANDLE:
- Race conditions on simultaneous checkout redemptions (use PostgreSQL SELECT FOR UPDATE on balance checks).
- Webhook duplicate deliveries from Shopify (strict unique constraints on order_id + transaction_type).

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