Pull Request: Favorites Functionality, UI Enhancements, and Email Verification

Description

This Pull Request includes the following features and improvements developed over the past two days:

Implemented the logic to add and remove cars from the favorites list:
Add to Favorites: When pressing a button in the car list, a car is added to the "Favorites" section in the database.
Remove from Favorites: The CheckBox was replaced with an "X" icon to remove cars from favorites. Removal refreshes the UI in real-time.
CarFavoritesAdapter: A new adapter was created to handle the favorites car list in the RecyclerView, supporting favorite car removal.
Added logic to check if a car is already in favorites when loading the car list.

Implemented a system to check if the user's email has been verified in Firebase before allowing them to proceed with registration:
The email verification status is checked every 1.5 seconds.
Added a "Retry" button to allow the user to manually force the verification process without waiting for the automatic check.
UI improvements to provide feedback to the user on the email verification status:
Success message shown once verified.
The "Continue" button is disabled until the email is verified.

Updated the UserViewModel to handle the logic for favorites and email verification:
Logic added to manage car data in real-time.
Function added to check if a car is already a favorite and update the UI accordingly.
Verification of the user's account status in Firebase to handle authentication and email verification.