Devlog 9 - Clear All Subjects Feature

I added a feature that allows users to remove all subjects at once.

Previously, subjects could only be removed one by one.
This worked fine for a small number of subjects, but it could become time consuming if a user wanted to start over with a new study plan.

To solve this, I added a Clear All Subjects button. When the button is clicked, all subject cards are removed from the page and the default empty message is shown again.

I also made sure that the saved data in local storage is cleared at the same time.
This prevents old subjects from coming back after refreshing the page.

After implementing the feature, I tested it with different numbers of subjects to make sure everything was removed correctly.