Migrate to Vue 3

[st3iny]

Is your feature request related to a problem? Please describe.

Contacts is a good candidate to pioneer migrating to Vue 3. Gained insights can then be used when migrating other Groupware apps.

Describe the solution you'd like

Contacts should be migrated to Vue 3. A concrete plan with actionable steps still has to be made.

Describe alternatives you've considered

None

Additional context

Let's wait for https://github.com/nextcloud/twofactor_webauthn/issues/712 to gain some insights.