fix(zer4moo): wire cart to Wix hosted checkout

[hanag-wix]

Summary

• Adds zer4moo/src/pages/api/checkout.ts — creates a Wix eCommerce checkout from custom line items (bouquet + delivery fee) via auth.elevate, then returns a hosted checkout URL through redirects.createRedirectSession
• Updates CartAndSend.tsx to POST cart lines to /api/checkout and redirect to Wix payment (fallback to /delivered if checkout creation fails)
• Adds @wix/ecom and @wix/redirects dependencies
• Updates root README table to list Wix eCommerce for Zer4moo

Based on hanag-wix/Zer4moo-with-wix-checkout — checkout-only changes; no adapter or unrelated refactors.

Checkout flow

1. Visitor builds bouquet → localStorage cart
2. /cart form submit → /api/checkout with line items
3. Redirect to Wix hosted checkout → thank-you at /delivered

Test plan

• cd zer4moo && npm install && npm run dev with linked Wix site
• Add bouquet to cart, fill delivery form, submit → redirects to Wix checkout
• Complete payment → returns to /delivered
• Site needs eCommerce app + payment provider configured in Wix Dashboard