Add custom validator to the `expired_time` DatePicker in `EditToken.js`
to ensure that selected expiration timestamps are strictly in the future.
- Introduce Promise-based validator that:
• Rejects invalid date formats with a clear error message
• Prevents past or current dates and shows “Expiration time cannot be earlier than the current time!”
- Keeps support for the special “never expires” value (-1)
- Blocks form submission until a valid future datetime is provided
This change prevents accidental creation of already expired tokens and
improves overall robustness of token management.
