Ability for admins / users to delete empty flights

[prphntm63]

Sometimes, users accidentally create extra flights. Having a delete functionality is critical to app flow and self-service.

Front End Requirements:

• Can only delete flights with no scoresheets
• Delete confirmation

Back End Requirements:

• Users should be blocked from deleting flights they did not create

[PH-Lazurous]

duplicate/elaboration of #34