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/Resources/Theme.xaml

@@ -3,6 +3,7 @@
                     xmlns:res="clr-namespace:PSLauncher.App.Resources">
 
     <BooleanToVisibilityConverter x:Key="BoolToVisibility" />
+    <res:InverseBoolToVisibilityConverter x:Key="InverseBoolToVisibility" />
 
     <!-- Custom font Pirulen pour les titres de marque -->
     <FontFamily x:Key="Font.Brand">pack://application:,,,/Resources/#Pirulen</FontFamily>
@@ -72,6 +73,47 @@
         </Setter>
     </Style>
 
+    <!--
+        NavButton : item de la sidebar de droite (Library / Report / Documentation).
+        Plein-largeur, alignement à gauche, pas de bordure, surligné quand actif
+        via Tag (bool) qui est lié à IsLibrary/IsReport/IsDocumentation.
+    -->
+    <Style x:Key="NavButton" TargetType="Button">
+        <Setter Property="Background" Value="Transparent" />
+        <Setter Property="Foreground" Value="{StaticResource Brush.Text.Secondary}" />
+        <Setter Property="FontSize" Value="13" />
+        <Setter Property="FontWeight" Value="SemiBold" />
+        <Setter Property="Padding" Value="20,12" />
+        <Setter Property="HorizontalContentAlignment" Value="Left" />
+        <Setter Property="HorizontalAlignment" Value="Stretch" />
+        <Setter Property="BorderThickness" Value="0" />
+        <Setter Property="Cursor" Value="Hand" />
+        <Setter Property="Template">
+            <Setter.Value>
+                <ControlTemplate TargetType="Button">
+                    <Border x:Name="Bd"
+                            Background="{TemplateBinding Background}"
+                            BorderThickness="3,0,0,0"
+                            BorderBrush="Transparent"
+                            Padding="{TemplateBinding Padding}">
+                        <ContentPresenter HorizontalAlignment="Left" VerticalAlignment="Center" />
+                    </Border>
+                    <ControlTemplate.Triggers>
+                        <Trigger Property="IsMouseOver" Value="True">
+                            <Setter TargetName="Bd" Property="Background" Value="#1A1F2A" />
+                        </Trigger>
+                        <!-- "Tag" est utilisé comme flag actif (IsLibrary/IsReport/IsDocumentation) -->
+                        <DataTrigger Binding="{Binding RelativeSource={RelativeSource Self}, Path=Tag}" Value="True">
+                            <Setter TargetName="Bd" Property="Background" Value="#1F2937" />
+                            <Setter TargetName="Bd" Property="BorderBrush" Value="{StaticResource Brush.Accent}" />
+                            <Setter Property="Foreground" Value="{StaticResource Brush.Text.Primary}" />
+                        </DataTrigger>
+                    </ControlTemplate.Triggers>
+                </ControlTemplate>
+            </Setter.Value>
+        </Setter>
+    </Style>
+
     <Style x:Key="PrimaryButton" TargetType="Button">
         <Setter Property="Background" Value="{StaticResource Brush.Play}" />
         <Setter Property="Foreground" Value="White" />