Bug 30650: Take dateformat into account

Bug 30650: Take dateformat into account

dayjs init was not passing the dateformat.
We really need to clean the date handling with the following two bugs:
  Bug 30310 - Replace Moment.js with Day.js
and
  Bug 30718 - Use flatpickr's altInput option everywhere

But it's outside the scope of this bug report.

Signed-off-by: Koha Team University Lyon 3 <koha@univ-lyon3.fr>
Signed-off-by: Katrin Fischer <katrin.fischer@bsz-bw.de>
Signed-off-by: Tomas Cohen Arazi <tomascohen@theke.io>