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/en-US.json

@@ -107,6 +107,11 @@
     "sentencePlaceholder": "Enter a sentence",
     "wordPlaceholder": "Enter a word",
     "queryLang": "Language",
+    "enterLanguageName": "Please enter language name",
+    "english": "English",
+    "chinese": "Chinese",
+    "japanese": "Japanese",
+    "korean": "Korean",
     "meanings": "Meanings",
     "addMeaning": "Add Meaning",
     "partOfSpeech": "Part of Speech",
@@ -268,6 +273,7 @@
       "ease": "Ease",
       "lapses": "Lapses",
       "showAnswer": "Show Answer",
+      "nextCard": "Next",
       "again": "Again",
       "hard": "Hard",
       "good": "Good",