feat(l10n): Add silence duration settings for speech-to-text

lib/l10n/app_localizations_en.dart

@@ -960,6 +960,13 @@ class AppLocalizationsEn extends AppLocalizations {
   String get sttServerUnavailableWarning =>
       'Connect to a server with transcription enabled to use this option.';
 
+  @override
+  String get sttSilenceDuration => 'Silence Duration';
+
+  @override
+  String get sttSilenceDurationDescription =>
+      'Time to wait after silence before auto-stopping recording';
+
   @override
   String get ttsEngineLabel => 'Engine';