Implement a function limit(fn, n) that restricts the execution of a given function to at most n times.

The function should:

• Return a new function that wraps the original function fn.
• Allow calls to fn only up to n times.
• After n calls, subsequent invocations should return undefined without executing fn.

Examples

function greet(name) { return 'Hello ' + name; }
const limitedGreet = limit(greet, 2);

limitedGreet('Alice'); // 'Hello Alice'
limitedGreet('Bob');   // 'Hello Bob'
limitedGreet('Carol'); // undefined