Update modal buttons to use correct design system variants (Meteor Admin Sdk)

### Technical TODO

## Problem
Modal buttons in the Meteor Admin SDK have incorrect variants, sizes, and types. They are based on the old `sw-button` component instead of the current design system.

## Goal
Align modal button styling with the current Meteor design system.

## Acceptance criteria
- [ ] Current modal button implementation is audited
- [ ] Modal buttons are updated to use correct button variants and sizes
- [ ] Consistency with the Meteor component library is ensured
- [ ] Different modal types are tested