Improve Quiz Quality: Fix Answer-Length Bias & Add Difficulty Levels

✨ What new feature or change would you like to see added in RemNote?
Please adjust the way multiple-choice answers are generated so that the correct answer isn't consistently the longest one. Also, consider adding difficulty levels (e.g. easy, medium, hard) or adaptive difficulty to the quizzes.

🤔 What problem does it solve for you? How would it improve your workflow or experience with RemNote?
Right now, it's often possible to guess the correct answer just by choosing the longest option — I tested this across several quizzes and it worked about 90% of the time. This undermines the effectiveness of the quizzes and reduces their learning value. Adding difficulty levels would also make quizzes more challenging and useful.