Draft: Port SettingsForm to Kirigami Addons mobile form

Reason for the change

Pros:

• Improves the usability of Elisa on mobile devices

Cons:

• Uses up way too much space on desktop (just compare the height of the screenshots below)

Marked as draft because

1. the form headings aren't looking how they should be (see e.g. NeoChat or Kalendar)
2. I think the "Music Folders" section could probably be converted into a more mobile style (and possible move to another page?)
3. Some form cards don't have a header yet. (I think it might be better to rearrange the settings first.)

Test plan

Run Elisa in desktop and mobile mode. Activate/change each setting.

Screenshots or screen recordings

Desktop:

Before	After

Mobile:

Before	After