feat(l10n): add English translation for 'Loading full list...'

- Add new localization string 'loadingFullList' to AppLocalizationsEn class
- This string can be used in the UI to indicate that a complete list is being loaded

Author: fulleni

lib/l10n/app_localizations_en.dart

@@ -695,6 +695,9 @@ class AppLocalizationsEn extends AppLocalizations {
   @override
   String get loadingData => 'Loading data...';
 
+  @override
+  String get loadingFullList => 'Loading full list...';
+
   @override
   String get createSource => 'Create Source';