Migrate to Vitest

[danieldanielecki]

as per https://blog.angular.dev/announcing-angular-v21-57946c34f14b in Angular v21 Vitest is the default test runner

[danieldanielecki]

First step done in 6502c05 where broken unit tests were fixed, Jest was removed, and native for Angular Jasmine + Karma was set as a testing framework.