Did a quick review of the new frontend testing documentation. 😄

Maybe we should do a quick test, where we follow these instructions to see if it's OK.
It might be that a step is confusing, incorrectly placed etc

Pull Request Overview

This PR introduces comprehensive documentation for frontend testing in OpenRemote using Playwright. The document provides detailed guidance on setting up and writing both end-to-end app tests and component tests.

• Establishes testing organization structure with separate configurations for app and component testing
• Documents prerequisites, setup steps, and best practices for Playwright testing
• Provides code examples and fixtures for both test types

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