Implement Todo API

[Matthewtizon]

Implemented a simple Todo REST API using Node.js and Express structured folder.

Features included:

• GET /api/todos - List all todos
• GET /api/todos/:id - Get a single todo
• POST /api/todos - Create a new todo
• PUT /api/todos/:id - Update a todo
• DELETE /api/todos/:id - Delete a todo

Each todo includes:

• id
• title
• completed
• createdAt

Added basic validation and error handling for invalid input, missing todos, and unknown routes.