Add Playwright tests for the workflow stepper / ENA picker

[NoopDog]

Overview

The workflow stepper is the most complex part of the application so far. Let's add some End-to-End Playwright tests to ensure it functions correctly.

• Come up with a backlog/wishlist of E2E tests.
• Select a basic set for implementation in this ticket.
• Let's discuss the backlog and use it to create a few more tasks in this area.

Consider sections for:

1. No workflow case
2. Workflow case