Add "Practice Failed Cards" Mode

[0010aor]

Description

Introduce a new practice mode specifically focused on the cards the user fails most often. This helps users target their weaker areas more effectively.

Current Behavior

• Users cannot automatically practice only their most frequently failed cards.

Expected Behavior

• An option is available to start a practice session containing only the cards identified as being frequently answered incorrectly.

[pedrosfaria2]

Hey! I'd like to start contributing to the project and work on this issue. Is that possible?

[0010aor]

Go ahead! Let me know if you have any question or need help, thanks!