Build a Todo API with Express

Problem/Feature Description

A small team needs a REST API for their todo application. The API should be built with Express and TypeScript. It will be consumed by a React frontend running on a separate domain. The backend will be deployed behind an nginx reverse proxy.

The API needs the following endpoints:

• GET /api/todos -- list all todos
• POST /api/todos -- create a new todo (accepts JSON body with title and optional description)
• PATCH /api/todos/:id -- update a todo (toggle completed, edit title)
• DELETE /api/todos/:id -- delete a todo

Use an in-memory array as the data store (no database required). Each todo should have id, title, description, completed, and createdAt fields.

Output Specification

Produce:

• app.ts -- Express application with all middleware and route setup
• routes/todos.ts -- Router module with the CRUD endpoint handlers
• package.json -- With all required dependencies