Retry decorator factory

Implement retry(times, exceptions=(Exception,)) — a decorator FACTORY that returns a decorator making fn retry up to times total attempts: - only the given exception types trigger a retry; anything else propagates immediately - if all attempts fail, re-raise the LAST exception - preserve the function's metadata: wrapped.__name__ == fn.__name__ - track attempts for observability: expose wrapped.attempts (list of ints, one entry per call)