i18n: localize all MessageBox dialogs

The previous batch only covered XAML strings. The runtime MessageBox
dialogs (errors, confirmations, info popups) stayed hardcoded in
French, breaking immersion for non-FR users.

Added ~15 keys to Strings.cs for the MessageBox bodies and titles:
- error / launch error / confirm / info / patience / language change /
  release notes (titles)
- launch failed / self-update failed / install failed / uninstall
  failed / uninstall confirm with version+folder+size / no release
  notes / fetch failed / clear cache confirm / deactivate license
  (short and detailed) / language restart (bodies)

Some are parametrized (MsgLaunchFailed(detail), MsgUninstallConfirm
(version, folder, size)) so the localized strings interpolate the
runtime values cleanly across all 5 languages.

Replaced every MessageBox.Show in MainViewModel, SettingsViewModel
and LicenseDetailsDialog.xaml.cs to use these keys. The "Échec : "
prefix in the cache-clear error was dropped — the error message alone
is sufficient with Strings.MsgBoxError as the dialog title.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/PSLauncher.App/Views/LicenseDetailsDialog.xaml.cs

@@ -1,6 +1,7 @@
 using System.Windows;
 using System.Windows.Media;
 using PSLauncher.Core.Licensing;
+using PSLauncher.Core.Localization;
 using PSLauncher.Models;
 
 namespace PSLauncher.App.Views;
@@ -66,10 +67,8 @@ public partial class LicenseDetailsDialog : Window
     private void OnDeactivate(object sender, RoutedEventArgs e)
     {
         var confirm = MessageBox.Show(
-            "Désactiver la license sur cette machine ?\n\n" +
-            "Tu pourras la réactiver plus tard avec ta clé. " +
-            "Les versions déjà installées restent utilisables.",
-            "Confirmer la désactivation",
+            Strings.MsgDeactivateLicenseDetailedConfirm,
+            Strings.MsgBoxConfirm,
             MessageBoxButton.YesNo, MessageBoxImage.Question, MessageBoxResult.No);
         if (confirm != MessageBoxResult.Yes) return;
         _licenseService.Clear();