e2e tests refactor

[ilicfilip]

This PR refactors e2e tests from JavaScript to TypeScript with Page Object Model pattern

• Migrated from Docker-based WordPress to WP Playground CLI for faster test execution
• Added custom Playwright fixtures for cleaner test setup and dependency injection
• CI jobs now run in parallel - main e2e tests and Yoast Premium tests start simultaneously
• All 9 original test files migrated with identical test coverage

Test Infrastructure

• WP Playground CLI: Replaces Docker for main e2e tests (~4x faster startup)
• Blueprint configuration: Pre-configures WordPress with test tokens and plugin activation
• Parallel CI jobs: e2e-tests and yoast-premium-tests run simultaneously
• Separate Yoast Premium job: Uses Docker (required for Composer/premium plugin installation)

[github-actions]

Test on Playground
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[github-actions]

✅ Code Coverage Report

Metric	Value
Total Coverage	31.53% 📉
Base Coverage	31.53%
Difference	📈 0.00%

⚠️ Coverage below recommended 40% threshold

🎉 Great job maintaining/improving code coverage!

ℹ️ About this report

• All tests run in a single job with Xdebug coverage
• Security tests excluded from coverage to prevent output issues
• Coverage calculated from line coverage percentages