* Change admin announcement edition interface to use datetime-local

* Dynamically set announcement stop date as required if start date is set, set minimum date for stop date

* Change `all_day` to not be bound to presence of time-range

* Add pattern and placeholder as minimal fallback for browsers not supporting datetime-local

* Display datetime-local inputs as local time

Co-authored-by: Eugen Rochko <eugen@zeonfederated.com>