test: add Playwright E2E testing infrastructure

[pcamarajr]

Summary

This PR sets up Playwright for end-to-end testing of the Rustalk web application. The infrastructure includes configuration, test suites for key user flows, CI integration, and documentation.

Changes

• Playwright Infrastructure: Added Playwright configuration with webServer setup for preview mode
• E2E Test Suites: Created initial test suites covering authentication, navigation, settings, and dialer functionality
• CI Integration: Added E2E test job to GitHub Actions workflow
• Documentation: Updated README with E2E testing instructions and usage

Testing

How to Test

1. Setup:

   git checkout test/e2e-testing-infrastructure-setup
   npm install

2. Test Steps:

   • Run E2E tests: npm test
   • Run with UI mode: npm run test:e2e:ui
   • Run in debug mode: npm run test:e2e:debug

3. Expected Behavior:

   • Tests should build the app and start preview server automatically
   • Tests should run against http://localhost:4173
   • All test suites should execute successfully
   • Test results should be available in playwright-report/

Test Coverage

• Unit tests added/updated (N/A - E2E tests only)
• Integration tests added/updated (E2E tests cover integration flows)
• Manual testing completed (tests can be run manually via npm scripts)
• Edge cases tested (basic edge cases in test suites)

Review Checklist

Code Quality

• Code follows project conventions
• Functions are focused and single-purpose
• Variable names are descriptive
• No code duplication
• Error handling is appropriate

Framework Compliance

• Svelte 5 runes mode (no legacy syntax) - N/A (test files are TypeScript)
• Rust code follows idiomatic patterns - N/A (no Rust changes)
• Tauri IPC follows best practices - N/A (no Tauri changes)
• Design system components used correctly - N/A (tests interact with DOM)

Security

• No hardcoded secrets
• Input validation present (test inputs are controlled)
• Sensitive data handled securely
• Tauri capabilities properly configured - N/A (no Tauri changes)

Documentation

• README.md updated (if applicable)
• Code comments explain complex logic
• Architecture docs updated (if applicable) - N/A (no architecture changes)

Breaking Changes

None

Related Issues

Implements E2E testing infrastructure as specified in the implementation plan.

Additional Notes

• Tests run against the built/preview version of the app (not dev server)
• Playwright automatically handles building and starting the preview server
• Browser binaries are installed via npx playwright install (not committed to repo)
• CI job runs E2E tests after frontend checks pass
• Test results are uploaded as artifacts in CI for debugging