Fix rejection email preview

[VineetBala-AOT]

Issue #: https://github.com/bcgov/met-public/issues/

Description of changes:

• Fix rejection email preview to use end date instead of scheduled date

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of the met-public license (Apache 2.0).

[marklise]

I would remove any 3rd party library like dayjs as they include an unnecessary dependency on the project. It can be achieved with built-in functions.

// Output similar to "Oct 14, 2025"
const endDate = new Date(survey.engagement?.end_date).toLocaleDateString('en-US', { month: 'short', day: '2-digit', year: 'numeric' });