Add automated testing PoC for Guard App login screen

[dhruvi-0406]

Implemented an automated testing proof of concept (PoC) for the Guard App using Jest and React Native Testing Library.

What was done:

• Set up Jest using the Expo testing preset (jest-expo)
• Added automated tests for the Login screen
• Verified UI rendering and basic user interaction using React Native Testing Library
• Simulated user actions using fireEvent
• Mocked AsyncStorage to resolve native module issues in the testing environment
• Added documentation under docs/Guard App Testing Stack PoC.pdf

Purpose:

This PoC demonstrates how automated testing can be integrated into the project in a simple and maintainable way. It provides a foundation that can be extended to cover more screens and features in the future. This implementation focuses on establishing a scalable testing setup rather than a complete testing framework.

[Krisha190235]

before we can approve this PR, there are a few important areas that need to be addressed:

Key concerns (must fix):
• The current tests are quite limited and don’t strongly validate behavior (e.g., assertions are too basic).
• There is no navigation-related test coverage.
• Some import formatting/spacing issues need to be cleaned up.

Improvements expected:
• Please strengthen the test cases (e.g., verify actual outcomes, not just rendering).
• Add at least one meaningful test that covers user flow (such as navigation or login success/failure).
• Include edge cases (e.g., invalid email, empty inputs).
• Consider using a reusable setup/helper function to reduce duplication.
• Double-check import paths (case sensitivity can cause issues across environments).

Also, can you please try to fix the Lint / ESLint & Prettier errors? There is a tutorial on Teams you can follow. If anything is unclear or you need help, please let me know — happy to help you through it.