Reject non-finite exp/nbf/iat values and tighten validation

[AzmeerX]

Description

1. Reject non-finite registered claim values (exp, nbf, iat) by tightening validation to require finite numbers.
2. Align tests to assert errors for Infinity, -Infinity, and NaN values instead of silently coercing them.
3. Keeps current API intact while preventing tokens with invalid temporal claims from being produced.

Testing

Commands run locally (Node v20.20.0 and above):
npm test -- test/claim-iat.test.js
npm test -- test/claim-nbf.test.js
npm test -- test/claim-exp.test.js
npm test

Checklist

All active GitHub checks for tests, formatting, and security are passing
The correct base branch is being used, if not the default branch

[AzmeerX]

let me know if you have any query about the commit or need any further change