Right sidebar nav: Library / Reports / Documentation tabs (WebView2)

The body of the launcher is now a 2-column layout:
- Left : swappable content area
- Right (200px) : sidebar with 3 nav buttons + active-state highlighting

Three pages, all under the same window chrome / footer:

1. **Library** (default) — the existing main view (featured version,
   other versions list, floating "Vérifier les MAJ" button, copyright).
2. **Reports** — embedded WebView2 navigated to a configurable URL.
   Default http://localhost/ProserveReport/ which matches the local
   stats tool installed on each customer machine alongside XAMPP.
3. **Documentation** — WebView2 with a configurable URL, falls back
   to a placeholder explaining where to set it if empty.

Implementation
- LocalConfig gains ReportUrl + DocumentationUrl (string).
- MainViewModel gains LauncherPage enum + CurrentPage state with
  Navigate{Library,Report,Documentation}Command. ReportUri /
  DocumentationUri parse the strings to Uri for WebView2.Source.
- Theme.xaml: NavButton style (transparent, left-aligned, hover
  darken, active state highlighted via Tag bool + accent left-border).
- InverseBoolToVisibilityConverter added (true → Collapsed) for the
  documentation placeholder fallback.
- Microsoft.Web.WebView2 NuGet (1.0.2792.45). Runtime is pre-installed
  on Win11 and auto-pushed via Windows Update on Win10. If absent,
  WebView2 surfaces an error which the user sees inline.
- Settings → Avancés → Serveur extended with the two URL fields.
- Strings.cs: NavLibrary / NavReport / NavDocumentation,
  SettingsReportUrl / SettingsDocsUrl, DocsPlaceholder, WebViewLoadError.
  Sidebar localized in 5 languages.

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

src/PSLauncher.App/PSLauncher.App.csproj

@@ -40,6 +40,11 @@
     <PackageReference Include="Serilog.Sinks.File" Version="6.0.0" />
     <PackageReference Include="Serilog.Sinks.Debug" Version="3.0.0" />
     <PackageReference Include="Microsoft.Toolkit.Uwp.Notifications" Version="7.1.3" />
+    <!-- WebView2 (Edge Chromium) pour les onglets Report et Documentation.
+         Le runtime est pré-installé sur Win11 et auto-mis-à-jour via Windows
+         Update sur Win10 récent. Si absent, le contrôle affiche une erreur
+         et on aiguille l'user vers https://go.microsoft.com/fwlink/p/?LinkId=2124703 -->
+    <PackageReference Include="Microsoft.Web.WebView2" Version="1.0.2792.45" />
   </ItemGroup>
 
   <ItemGroup>