feat: add redo functionality for failed exam questions and update translations

frontend/src/components/Results.tsx

@@ -12,10 +12,11 @@ interface Props {
   state: ExamState
   onRestart: () => void
   onExit: () => void
+  onRedoFailed?: () => void
   reviewOnly?: boolean
 }
 
-export default function Results({ exam, state, onRestart, onExit, reviewOnly }: Props) {
+export default function Results({ exam, state, onRestart, onExit, onRedoFailed, reviewOnly }: Props) {
   const { t } = useTranslation()
   const { answers, startedAt, completedAt } = state
   const elapsedMs = (completedAt ?? Date.now()) - startedAt
@@ -30,6 +31,7 @@ export default function Results({ exam, state, onRestart, onExit, reviewOnly }:
   const scorePoints = graded.reduce((a, g) => a + g.result.points, 0)
   const gradedCount = graded.filter((g) => g.result.status !== 'ungraded').length
   const correctCount = graded.filter((g) => g.result.correct).length
+  const failedCount = gradedCount - correctCount
   const pct = totalPoints ? Math.round((scorePoints / totalPoints) * 100) : 0
   const passing = exam.passingScore ?? 60
   const passed = pct >= passing
@@ -137,7 +139,16 @@ export default function Results({ exam, state, onRestart, onExit, reviewOnly }:
       })}
 
       <div style={{ marginTop: 48, display: 'flex', gap: 12 }}>
-        {!reviewOnly && <button className="btn btn-primary" onClick={onRestart}>{t('results.retakeExam')}</button>}
+        {!reviewOnly && (
+          <>
+            <button className="btn btn-primary" onClick={onRestart}>{t('results.retakeExam')}</button>
+            {onRedoFailed && failedCount > 0 && (
+              <button className="btn" onClick={onRedoFailed}>
+                {t('results.redoFailed')}
+              </button>
+            )}
+          </>
+        )}
         <button className="btn" onClick={onExit}>{t('results.backToHome')}</button>
       </div>
     </div>