e2e tests: Add Automated testing for "Add Cluster Scenario"

See scenario video in chat if you don't know the scenario well.
See the headlamp e2e app tests, and parent issue for more instructions.

- [ ] e2e test that runs locally
- [ ] Make sure a11y is enabled in each playwright tests like Headlamp
- [ ] e2e test that runs ok in CI

Start by reading the Headlamp e2e app tests and the parent issue, then review the scenario video referenced in chat for the Add Cluster flow. Identify the existing Playwright test entry points and how accessibility is enabled. Done means the scenario runs locally, accessibility is enabled in each relevant test, and the suite passes in CI.

Written by the indexing model from the issue text.