Improve E2E Playwright test suite for tmail

[hoangdat]

Desc

The mail test suite demonstrates good foundational architecture (Page Object Model, TypeScript types, environment config) but suffers from critical implementation issues that severely impact reliability, maintainability, and performance.

Critical issues:

1. No Test Data Cleanup
2. Excessive Hardcoded Waits
3. No isolation test
4. Code duplication
5. Fragile XPath locators

DoD

• Refactoring tests to address all critical issues to make it easier to maintain