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/ja-JP.json

@@ -133,6 +133,11 @@
     "sentencePlaceholder": "文章を入力",
     "wordPlaceholder": "単語を入力",
     "queryLang": "検索言語",
+    "enterLanguageName": "言語名を入力してください",
+    "english": "英語",
+    "chinese": "中国語",
+    "japanese": "日本語",
+    "korean": "韓国語",
     "meanings": "意味",
     "addMeaning": "意味を追加",
     "partOfSpeech": "品詞",
@@ -265,6 +270,7 @@
       "ease": "易しさ",
       "lapses": "忘回数",
       "showAnswer": "答えを表示",
+      "nextCard": "次へ",
       "again": "もう一度",
       "hard": "難しい",
       "good": "普通",