feat: add study modes to Memorize page

- Add 4 study modes: order-limited, order-infinite, random-limited, random-infinite
- Add mode selector buttons with icons
- Update progress display for infinite modes
- Add translations for all 8 locales

messages/de-DE.json

@@ -233,32 +233,11 @@
       "showAnswer": "Antwort zeigen",
       "nextCard": "Weiter",
       "again": "Nochmal",
-      "hard": "Schwer",
-      "good": "Gut",
-      "easy": "Leicht",
-      "now": "Jetzt",
-      "lessThanMinute": "weniger als 1 Minute",
-      "inMinutes": "in {n} Minute{n, plural, one {} other {n}}",
-      "inHours": "in {n} Stunde{n, plural, one {} other {n}}",
-      "inDays": "in {n} Tag{en}",
-      "inMonths": "in {n} Monat{en}",
-      "minutes": "Minuten",
-      "days": "Tage",
-      "months": "Monate",
-      "minAbbr": "min",
-      "dayAbbr": "d",
-      "cardTypeNew": "Neu",
-      "cardTypeLearning": "Lernen",
-      "cardTypeReview": "Wiederholen",
-      "cardTypeRelearning": "Neu lernen",
-      "reverse": "Umkehren",
-      "dictation": "Diktat",
-      "clickToPlay": "Klicken zum Abspielen",
-      "yourAnswer": "Ihre Antwort",
-      "typeWhatYouHear": "Schreiben Sie was Sie hören",
-      "correct": "Richtig!",
-      "incorrect": "Falsch",
-      "nextCard": "Nächste"
+      "modeOrderLimited": "Reihenfolge",
+      "modeOrderInfinite": "Schleife",
+      "modeRandomLimited": "Zufällig",
+      "modeRandomInfinite": "Zufällig Schleife",
+      "restart": "Neustart"
     },
     "page": {
       "unauthorized": "Nicht autorisiert"