Solution (#100): [BUG] - Instant update of favorited images

[TFGSUMIT]

"This PR fixes the issue of instant update of favorited images not working as expected in the Fossify Gallery app. The changes involve adding a notifyUI method to MediaFetcher, creating a FavoriteViewModel, and updating the PhotoFragment to use the new ViewModel.

To test this PR, follow these steps:

1. Clone the repository and checkout the latest code.
2. Run the app on an Android 10 or 11 device.
3. Mark an image as favorite and observe the UI update.
4. Verify that the UI updates in real-time when a user marks an image as favorite.

Changes made:

• Added a notifyUI method to MediaFetcher to notify the UI when a user marks an image as favorite.
• Created a FavoriteViewModel to handle the favorite medium logic.
• Updated the PhotoFragment to use the new ViewModel.

Testing instructions:

• Run the app on an Android 10 or 11 device.
• Mark an image as favorite and observe the UI update.
• Verify that the UI updates in real-time when a user marks an image as favorite."