Timepicker: allow specifying timezone in timestamp fields

<img width="340" height="250" alt="Image" src="https://github.com/user-attachments/assets/bd40b832-3934-483a-b8c1-b5de053b83c1" /> ↑ The current behavior is that `+00:00` is truncated without any time adjustment. **Why is this needed**: It's cumbersome for users to adjust the hours or minutes to match the selected timezone in the picker. **What would you like to be added**: The timepicker should be able to resolve the timezone part of the ISO 8601 timestamp. **Who is this feature for?** Anyone interacting with the timepicker