Innføre Playwright for testing

For å kunne teste løsningen (frontend) kan vi innføre Playwright (https://playwright.dev). Dette vil gjøre at vi kan kjøre tester lokalt for å verifisere at ting kjører som det skal. På sikt kan vi også legge inn Playwright som et bygg-steg.

- E2E-testing av løsningen
- WCAG-testing

Start by reviewing the frontend and the Playwright documentation linked in the issue. Define how local end-to-end tests and WCAG checks should run, then verify that the resulting tests can be run locally against the solution; adding a build step is described as a later possibility.

Written by the indexing model from the issue text.