feat: confirm before leaving a game, and fix untranslated strings

Exit confirmation
- A dialog in the app's own style now guards every in-game screen. The safe
  action is the prominent one, so a stray tap keeps you in the game.
- Eleven screens covered, against both the system back gesture and the close
  buttons. The message adapts: a single-device game is lost, a host ends it
  for everyone, a client can rejoin.
- The two screens the host also opens from the manager take a flag so that
  back there just closes them instead of offering to quit.

Translations
- 21 keys were still holding the English text in Arabic, Basque, Hindi,
  Japanese, Korean, Dutch, Polish, Russian, Turkish and both Chinese
  variants: 231 strings, covering the whole multi-device flow, permissions
  and the mode picker. Nothing failed, the app just showed English.
- The permissions dialog was hardcoded in Spanish; it is localized now.
- Portuguese used Spanish gerunds where pt-PT takes "a + infinitive".

Checked what looked untranslated but is not: Animals and Notes are correct
Catalan, Configuration and Vibration correct French, Version correct German.
Those are whitelisted in the new test rather than silently rewritten.

l10n_cobertura_test guards all of it: no missing or orphan keys, no empty
values, no English left outside the whitelist, and placeholders preserved.

lib/l10n/generated/app_localizations_nl.dart

@@ -655,83 +655,83 @@ class AppLocalizationsNl extends AppLocalizations {
 
   @override
   String get selectAtLeastThreeUsersToStart =>
-      'Select at least 3 users to start.';
+      'Selecteer minstens 3 gebruikers om te starten.';
 
   @override
   String get hostPhoneMustSelectUser =>
-      'The host phone must select at least one user.';
+      'De host-telefoon moet minstens één gebruiker selecteren.';
 
   @override
-  String get roomNoLongerInLobby => 'The room is no longer in the lobby.';
+  String get roomNoLongerInLobby => 'De ruimte is niet meer in de lobby.';
 
   @override
   String get completeUserSelectionToStart =>
-      'Complete user selection to start.';
+      'Voltooi de gebruikersselectie om te starten.';
 
   @override
-  String get preparingSecureRoom => 'Preparing the secure room';
+  String get preparingSecureRoom => 'Beveiligde ruimte voorbereiden';
 
   @override
   String get searchingNearbyBluetoothGames =>
-      'Searching nearby games over Bluetooth';
+      'Zoeken naar spellen in de buurt via Bluetooth';
 
   @override
-  String get tapToJoin => 'Tap to join';
+  String get tapToJoin => 'Tik om deel te nemen';
 
   @override
   String get bluetoothLocationPermissionsRequired =>
-      'Bluetooth and location permissions are required to search for games.';
+      'Bluetooth- en locatietoestemming zijn nodig om spellen te zoeken.';
 
   @override
   String get bluetoothLocationPermissionsShort =>
-      'Bluetooth and location permissions are required';
+      'Bluetooth- en locatietoestemming zijn nodig';
 
   @override
   String get couldNotStartSearch =>
-      'Could not start the search. Check Bluetooth and location.';
+      'Kon het zoeken niet starten. Controleer Bluetooth en locatie.';
 
   @override
   String couldNotConnectToHost(String host) {
-    return 'Could not connect to $host';
+    return 'Kon geen verbinding maken met $host';
   }
 
   @override
   String get room => 'Kamer';
 
   @override
-  String get singleDeviceSubtitle => 'Game on this device';
+  String get singleDeviceSubtitle => 'Spel op dit toestel';
 
   @override
   String get singleDeviceDescription =>
-      'Ideal for playing together by passing the phone around. Fast, direct setup.';
+      'Ideaal om samen te spelen door de telefoon door te geven. Snel en direct ingesteld.';
 
   @override
-  String get multiDeviceSubtitle => 'Each player on their phone';
+  String get multiDeviceSubtitle => 'Elke speler op zijn eigen telefoon';
 
   @override
   String get multiDeviceDescription =>
-      'Create a premium room, share the QR code and manage users from the lobby.';
+      'Maak een premium ruimte, deel de QR-code en beheer gebruikers vanuit de lobby.';
 
   @override
-  String get singleDeviceGameLabel => 'Game on this device';
+  String get singleDeviceGameLabel => 'Spel op dit toestel';
 
   @override
-  String get multiDeviceGameLabel => 'Multi-device game';
+  String get multiDeviceGameLabel => 'Spel met meerdere toestellen';
 
   @override
-  String get mainDeviceUser => 'Main device user';
+  String get mainDeviceUser => 'Hoofdgebruiker van dit toestel';
 
   @override
   String get couldNotCreateRoom =>
-      'Could not create the room. Check Bluetooth.';
+      'Kon de ruimte niet aanmaken. Controleer Bluetooth.';
 
   @override
   String cannotStartWithReason(String reason) {
-    return 'Cannot start: $reason';
+    return 'Kan niet starten: $reason';
   }
 
   @override
-  String get invalidRoom => 'invalid room';
+  String get invalidRoom => 'ongeldige ruimte';
 
   @override
   String get defaultPlayerName => 'Speler';
@@ -845,4 +845,50 @@ class AppLocalizationsNl extends AppLocalizations {
   String playerRejoined(String name) {
     return '$name is terug in het spel';
   }
+
+  @override
+  String get leaveGameTitle => 'Het spel verlaten?';
+
+  @override
+  String get leaveGameSingleDevice =>
+      'Het lopende spel gaat verloren en kan niet worden hersteld.';
+
+  @override
+  String get leaveGameHost =>
+      'Jij bent de host: als je weggaat, eindigt het spel voor iedereen.';
+
+  @override
+  String get leaveGameClient =>
+      'Je verlaat het spel. Je kunt terugkomen zolang de host het openhoudt.';
+
+  @override
+  String get stayInGame => 'Verder spelen';
+
+  @override
+  String get permissionsNeededTitle => 'Toestemmingen nodig';
+
+  @override
+  String get permissionsNeededBody =>
+      'Voor de multiplayermodus hebben we nodig:';
+
+  @override
+  String get openAppSettingsQuestion => 'De app-instellingen openen?';
+
+  @override
+  String get openSettings => 'Instellingen openen';
+
+  @override
+  String get permissionLocation => 'Locatie';
+
+  @override
+  String get permissionBluetoothAdvertise => 'Bluetooth (zichtbaar maken)';
+
+  @override
+  String get permissionBluetoothConnect => 'Bluetooth (verbinden)';
+
+  @override
+  String get permissionBluetoothScan => 'Bluetooth (scannen)';
+
+  @override
+  String get permissionNearbyWifi => 'Wi-Fi in de buurt';
 }