Deck settings reorganization

Reorganized settings using the new form components. See https://github.com/nextcloud/server/issues/55667

The app should also use a dialog for settings.

<img width="500" height="226" alt="Image" src="https://github.com/user-attachments/assets/5c3c5e20-7680-43ac-849d-73cd8a05146c" />