fix: Reset deadline state on error and add upload timing logs

fix: correct timeRemaining variable in countdown timer

feat: rewrite QuizPlayer with clean single-page UI and fix PDF upload FormData

fix: Enable quiz scroll and increase API timeout to 3 minutes

fix: Enable scroll in QuizPlayer modal

fix: Remove dead code from pagination mode conversion

feat: Convert QuizPlayer to single-page scroll mode

fix: Update countdown timer to use ref for non-retriggering updates

fix: Consistent error messages and archive terminology across quiz components

fix: Improve quiz error messages and modal overflow handling

feat: Fix countdown timer, rename quiz list, and add sorting

fix: Add clock skew buffer and better deadline error handling

fix: Fix quiz deadline bug and add user profile names in results

feat: Cải thiện đầy đủ hệ thống quiz

fix: Chữa timezone và tránh flash khi reload quiz

feat: Thêm countdown timer và deadline validation cho quiz

feat: add QuizResults component for displaying quiz results and analytics