Refactor CozyAppScreen and Extract UI Logic to useUIState Hook

[acezard]

This pull request aims to improve the maintainability and modularity of the CozyAppScreen component by separating its UI-related logic and state management. The main changes introduced in this PR are:

1. Extracted UI-related logic and state management from the CozyAppScreen component into a custom hook called useUIState.
2. Updated the useUIState hook to handle UIState updates correctly.
3. Added TypeScript types for the useUIState hook and the CozyAppScreen component.
4. Created a Jest test suite for the useUIState hook to ensure its functionality.
5. Added documentation for the useUIState hook and the CozyAppScreen component to help developers understand their usage.

By extracting the UI-related logic to a separate hook, we've made the code more modular and easier to maintain. The added tests and documentation further ensure that the new code is robust and well-understood.

[acezard]

#771