feat: add retake attempt functionality and update translations for retake button

frontend/src/i18n/en.json

@@ -39,6 +39,7 @@
     "clearHistory": "Clear history",
     "dateTimeFormat": "{{date}} · {{correct}}/{{graded}} correct",
     "review": "Review",
+    "retake": "Retake",
     "loadError": "Could not load: {{message}}",
     "loadSampleError": "Could not load sample: {{message}}",
     "clearHistoryConfirm": "Clear all past attempts?"