Payment Processing Endpoint

Problem Description

Build a POST /api/payments endpoint for a small billing service. The endpoint accepts a JSON body with { customerId, amount, currency } and creates a payment record. In a real system this would charge the customer's card, but for this exercise just store the payment in a SQLite database and return the record.

Output Specification

Produce:

1. A server.js (or server.ts) file with an Express app that:

   • Creates a SQLite database using better-sqlite3 with a payments table
   • Has a POST /api/payments route that accepts { customerId, amount, currency } and inserts a payment record
   • Returns the created payment as JSON with a 201 status code
   • Listens on port 3000

2. A schema.sql file containing the DDL for the payments table.

The service should be production-quality — handle errors properly, validate inputs, and follow best practices for a financial endpoint.