Add localization for chat and repeater features in multiple languages

- Added translations for "Send message", "Guest information", and "Guest tools" in Bulgarian, German, Spanish, French, Hungarian, Italian, Japanese, Korean, Dutch, Polish, Portuguese, Russian, Slovak, Slovenian, Swedish, Ukrainian, and Chinese.
- Updated the "Clock synchronization after login" feature subtitle in all affected languages.
- Removed untranslated keys from the untranslated.json file as they have now been localized.

lib/l10n/app_localizations_ja.dart

@@ -1180,7 +1180,7 @@ class AppLocalizationsJa extends AppLocalizations {
   String get chat_noMessages => 'まだメッセージは届いていません';
 
   @override
-  String get chat_sendMessage => 'Send message';
+  String get chat_sendMessage => 'メッセージを送信する';
 
   @override
   String chat_sendMessageTo(String contactName) {
@@ -1933,16 +1933,16 @@ class AppLocalizationsJa extends AppLocalizations {
   String get room_management => 'ルームサーバーの管理';
 
   @override
-  String get repeater_guest => 'Repeater Information';
+  String get repeater_guest => '繰り返し送信に関する情報';
 
   @override
-  String get room_guest => 'Room Server Information';
+  String get room_guest => 'ルームサーバーに関する情報';
 
   @override
   String get repeater_managementTools => '管理ツール';
 
   @override
-  String get repeater_guestTools => 'Guest Tools';
+  String get repeater_guestTools => 'ゲスト向けツール';
 
   @override
   String get repeater_status => 'ステータス';