Build a Payment Processing API

Problem/Feature Description

An e-commerce company needs a REST API to process payments through Stripe and store order records in PostgreSQL. Build it using Express and TypeScript.

Endpoints:

• POST /api/payments -- create a payment intent (amount, currency, customer email)
• GET /api/payments/:id -- retrieve payment status
• GET /api/payments -- list payments with optional ?status= filter
• POST /api/webhooks/stripe -- receive Stripe webhook events to update payment status

Business rules:

• Amount must be a positive integer (in cents)
• Currency must be a supported ISO code (usd, eur, gbp)
• Customer email is required and must be valid
• Webhook endpoint must verify Stripe's signature before processing

Use pg for PostgreSQL and stripe for Stripe integration.

Output Specification

Produce:

• src/server.ts -- server entry point
• src/app.ts -- Express application setup
• src/routes/payments.ts -- payment route handlers
• src/routes/webhooks.ts -- Stripe webhook handler
• src/db.ts -- database connection and queries
• package.json -- with dependencies listed (no need to run npm install)
• .gitignore -- standard Node.js gitignore

You may create additional files as needed for a well-structured codebase.