v0.16.0 — ThemedMessageBox replacing native MessageBox everywhere

The Win32 MessageBox uses the system white-on-gray look that clashes
with the launcher's dark theme (jarring transition every time we
confirm a cancel, show an error, etc.). Replaced with a custom WPF
dialog that:

- Drops in : same Show(message, title, button, icon, default) API as
  System.Windows.MessageBox, returns the same MessageBoxResult.
- Looks native to the launcher : dark Brush.Bg.Window background,
  Brush.Border outline, Brush.Text.Primary content, AccentButton for
  the default action and SecondaryButton for the others.
- Iconography by emoji + colour code : ⛔ red (Error), ⚠ amber (Warning),
  ❓ neutral (Question), ℹ blue (Information). Mapped from MessageBoxImage.
- Buttons localised via Strings.ActionOk / ActionYes / ActionNo /
  ActionCancel — works in fr/en/zh/th/ar like the rest of the UI.
- Owner = currently active window (falls back to MainWindow then
  CenterScreen) so it positions correctly even from a child dialog.
- Esc resolves to Cancel/No matching MessageBox semantics.

The 21 MessageBox.Show call sites across MainViewModel, SettingsViewModel,
LicenseDetailsDialog and MainWindow now use ThemedMessageBox.Show with
no signature change — full grep replace + tiny `using` adjustments.

Versions bumped to 0.16.0.

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

src/PSLauncher.App/PSLauncher.App.csproj

@@ -15,9 +15,9 @@
     <Product>PROSERVE Launcher</Product>
     <Copyright>© 2026 ASTERION VR — All rights reserved</Copyright>
     <RootNamespace>PSLauncher.App</RootNamespace>
-    <Version>0.15.0</Version>
-    <AssemblyVersion>0.15.0.0</AssemblyVersion>
-    <FileVersion>0.15.0.0</FileVersion>
+    <Version>0.16.0</Version>
+    <AssemblyVersion>0.16.0.0</AssemblyVersion>
+    <FileVersion>0.16.0.0</FileVersion>
 
     <!-- Single-file self-contained publish profile (used by `dotnet publish`) -->
     <PublishSingleFile>true</PublishSingleFile>