test: add playwright end to end test

[TorunW]

Closes #12

Summary

This PR adds Playwright end-to-end testing support for the project and integrates E2E testing into the CI workflow.

Changes made

• Added @playwright/test to frontend dev dependencies

• Created playwright.config.ts

• Configured Playwright to start the backend/server when running tests

• Added a test:e2e script to package.json

• Added GitHub Actions workflow configuration in .github/workflows/playwright.yml

• Added README documentation for running E2E tests locally:

  cd frontend && pnpm test:e2e

• Added initial Playwright E2E tests:

  • Verifies the backend health status is displayed correctly
  • Verifies the page title is rendered correctly

Tests added

• Homepage title validation
• Backend health endpoint/status rendering validation

Goal

This enables automated end-to-end testing of the full stack application in CI using Playwright.