i18n: full pass + culture-aware dates/sizes + Software Update License wording

- Strings.cs : ~80 new keys covering status messages, progress detail
  (DL/extraction/verify), license summary, license details dialog, onboarding
  statuses, settings field labels, restart/cancel/quit confirmations, toasts,
  resume choice, copyright. Strings.FormatSize and Strings.FormatDate /
  FormatLongDate switch units (o/Ko vs B/KB) and pattern (dd/MM/yyyy vs M/d/yyyy
  vs 2026年) by active language.
- License terminology renamed across UI: "License" → "License de mise à jour"
  / "Software Update License" to clarify it gates UPDATES, not Proserve itself.
  Expired/revoked dialogs now spell out "you can still download versions
  released before this date and launch any installed version".
- "🔒 License insuffisante" → "🔒 License de mise à jour requise pour cette
  version" / "Valid update license needed for this version" so users understand
  it's a per-version eligibility check, not a global block.
- All hardcoded FR strings in views (SettingsDialog labels, LicenseDetails
  fields, Onboarding statuses, dialog titles, copyright, window chrome
  tooltips, "Sortie le", etc.) replaced with x:Static loc bindings.
- All FormatSize duplicates (5 places) and date format strings (8 places)
  delegate to Strings helpers — single source of truth for localization.
- Settings dialog: License section moved to the top before Language. It's
  the most important info and conditions what the user can download.

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

src/PSLauncher.App/ViewModels/InstalledVersionViewModel.cs

@@ -1,3 +1,4 @@
+using PSLauncher.Core.Localization;
 using PSLauncher.Models;
 
 namespace PSLauncher.App.ViewModels;
@@ -11,17 +12,7 @@ public sealed class InstalledVersionViewModel
     public string Display => $"v{Model.Version}";
 
     public string Subtitle =>
-        $"{FormatSize(Model.SizeBytes)} • Installée le {Model.InstalledAt.ToLocalTime():dd/MM/yyyy}";
-
-    private static string FormatSize(long bytes)
-    {
-        if (bytes <= 0) return "—";
-        string[] units = { "o", "Ko", "Mo", "Go", "To" };
-        double v = bytes;
-        int u = 0;
-        while (v >= 1024 && u < units.Length - 1) { v /= 1024; u++; }
-        return $"{v:0.#} {units[u]}";
-    }
+        $"{Strings.FormatSize(Model.SizeBytes)} • {Strings.FormatDate(Model.InstalledAt)}";
 
     public override string ToString() => Display;
 }

src/PSLauncher.App/ViewModels/SettingsViewModel.cs

@@ -52,11 +52,12 @@ public sealed partial class SettingsViewModel : ObservableObject
         get
         {
             var l = _licenseService.GetCached();
-            if (l is null) return "Aucune license activée — clique pour saisir une clé";
+            if (l is null) return Strings.LicenseSummaryNone;
             if (l.Status == "valid")
-                return $"{l.OwnerName} • valable jusqu'au {l.DownloadEntitlementUntil:dd/MM/yyyy}";
+                return Strings.LicenseSummaryValid(l.OwnerName ?? "—",
+                    Strings.FormatDate(l.DownloadEntitlementUntil));
             if (l.Status == "expired")
-                return $"{l.OwnerName} • expirée le {l.DownloadEntitlementUntil:dd/MM/yyyy}";
+                return Strings.LicenseSummaryExpired(Strings.FormatDate(l.DownloadEntitlementUntil));
             return $"{l.OwnerName} • {l.Status}";
         }
     }
@@ -159,7 +160,7 @@ public sealed partial class SettingsViewModel : ObservableObject
     {
         var dlg = new Microsoft.Win32.OpenFolderDialog
         {
-            Title = "Choisir le dossier d'installation",
+            Title = Strings.SettingsInstallRoot,
             InitialDirectory = Directory.Exists(InstallRoot) ? InstallRoot : Environment.GetFolderPath(Environment.SpecialFolder.UserProfile),
         };
         if (dlg.ShowDialog() == true)
@@ -287,12 +288,5 @@ public sealed partial class SettingsViewModel : ObservableObject
         catch { CacheSizeDisplay = "—"; }
     }
 
-    private static string FormatSize(long bytes)
-    {
-        if (bytes <= 0) return "0 o";
-        string[] units = { "o", "Ko", "Mo", "Go", "To" };
-        double v = bytes; int u = 0;
-        while (v >= 1024 && u < units.Length - 1) { v /= 1024; u++; }
-        return $"{v:0.#} {units[u]}";
-    }
+    private static string FormatSize(long bytes) => Strings.FormatSize(bytes);
 }