Build a User Registration and Login API

Problem/Feature Description

A startup needs a user authentication API built with Express and TypeScript. The API will handle user signup and login using JWT tokens. A React single-page app on a separate domain will consume this API.

The API needs the following endpoints:

• POST /api/auth/register -- create a new user account (accepts email, username, password)
• POST /api/auth/login -- authenticate and return a JWT token
• GET /api/auth/me -- return the current user's profile (requires valid JWT in Authorization header)

Use bcrypt for password hashing and jsonwebtoken for JWT creation/verification. Store users in an in-memory array (no database required). The JWT secret should come from an environment variable.

Output Specification

Produce:

• app.ts -- Express application entry point with middleware and route wiring
• routes/auth.ts -- Router module with register, login, and profile endpoints
• middleware/authenticate.ts -- JWT verification middleware for protected routes
• package.json -- With all required dependencies