Update schedule edit: Add backdrop

Add a dark backdrop to the schedule editor just like with rcc-pull-down-select. That's it :)

There are two places where it shows up (one already has the backdrop):

• (needs backdrop) in HCP variant -> 'Therapie FollowUp' -> Select 'Depression' -> edit a question -> click 'Individuellen zeitplan setzen'
• (has backdrop) in HCP variant -> 'Therapie FollowUp' -> Select 'Depression' -> goto 'Standardzeitplan & Erinnerung'

Where to start?

the bottom -> click 'täglich'

• @rcc/features/monitoring-setup/modal/edit-schedule/edit-schedule-modal.component.ts