Shift Time Validation
Creating a shift with end time before start time shows an error
Navigate to the new shift form
and fill in an end time before the start time.
The error appears as soon as both times are set — you don't have to submit to find out.
Submitting is blocked while the error stands.
Editing a shift with end time before start time shows an error
Set the end time before the start time.
An error is shown and submitting is blocked.
