fix: add missing translations and fix namespace usage

- Fix srt-player to use srtT namespace for error messages
- Add deck_id.enterLanguageName and language labels (english, chinese, japanese, korean)
- Add memorize.review.nextCard translation
- Update all 8 locales with consistent translations

messages/it-IT.json

@@ -165,6 +165,11 @@
     "sentencePlaceholder": "Inserisci frase",
     "wordPlaceholder": "Inserisci parola",
     "queryLang": "Lingua di query",
+    "enterLanguageName": "Inserisci il nome della lingua",
+    "english": "Inglese",
+    "chinese": "Cinese",
+    "japanese": "Giapponese",
+    "korean": "Coreano",
     "meanings": "Significati",
     "addMeaning": "Aggiungi significato",
     "partOfSpeech": "Parte del discorso",
@@ -297,6 +302,7 @@
       "ease": "Difficoltà",
       "lapses": "Errori",
       "showAnswer": "Mostra risposta",
+      "nextCard": "Prossima",
       "again": "Ancora",
       "hard": "Difficile",
       "good": "Buono",