Added unit tests

[atsi2004]

Description:
Added comprehensive unit tests for existing screens and components. Highlights include:

• Added Jest tests for CreateAccount, CreateStac, ForgetPassword, HomePage, Landing, Login, Profile, SignUpQuestions, and StacForm.
• Updated screen components to improve testability where needed.
• Coverage is roughly ~70% on all files except HomePage.tsx and StacForm.tsx who still need additional tests for full coverage.
• Includes setup for Jest (jest.setup.js and jest.config.js).
• All tests run successfully via npm test.

Testing Instructions:

• Install dependencies if needed: npm install
• Run all tests: npm test
• Confirm all tests pass without warnings

[cpjreynolds]

Looks good. I'll need to rebase this on top of the changes I made to the backend-calling code before merging