fix: replace date() with gmdate() and rand() with wp_rand()

[masteradhoc]

All Submissions:

• Have you followed the Contributing guidelines?
• Does your code follow the WordPress' coding standards?
• Have you checked to ensure there aren't other open Pull Requests for the same update/change?

Changes proposed in this Pull Request:

Replace PHP native date() with WordPress's gmdate() and rand() with wp_rand() across Settings.php and Order.php.

• date() is affected by the server's runtime timezone and can produce inconsistent timestamps depending on the environment. gmdate() always outputs UTC, which is what WordPress expects internally.
• rand() is PHP's native PRNG and is flagged by WordPress coding standards. wp_rand() is the recommended drop-in replacement.

These changes resolve 12 PHPCS errors (WordPress.DateTime.RestrictedFunctions.date_date and WordPress.WP.AlternativeFunctions.rand_rand) and move towards resolving #209.

Related to #209.

Other information:

• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes, as applicable?
• Have you successfully run tests with your changes locally?

Changelog entry

Replace date() with gmdate() and rand() with wp_rand() to comply with WordPress coding standards and ensure timezone-safe date output.

FOR PR REVIEWER ONLY:

• I have reviewed that everything is sanitized/escaped appropriately for any SQL or XSS injection possibilities. I made sure Linting is not ignored or disabled.