Validation for service hours

In #3740, we set up logic for service hours that are the same as locations. But for one of our test cases:
- Add a service and neither marked it as `The hours for this service are the same as the location hours` nor add hours
we implemented an MVP solution that, in this scenario, Janis doesn't show the hours section on the related service, leading to this:

We could instead have smarter validation in Joplin that makes it required to either enter service hours or check the box.

@easherma started to do some work to this effect on this PR:

> https://joplin-pr-3740-with-validation.herokuapp.com/admin/login/ exposes the validation errors so you can see what it looks like (introduces a small regression on the search field which I have an idea of a fix for)

But we'll want to fully define acceptance criteria and test cases to make this happen. We'll also want to use this as an opportunity to think through the user experience.