v0.18.0 — Bluer dark palette to match ASTERION VR identity

Shifts the launcher background from pure black to deep navy and adds a
subtle blue tint over the body bitmap so the overall feel is closer to
the brand's blue/cyan accent rather than neutral black-on-grey.

Theme.xaml palette tweaks
- Brush.Bg.Window  : #000000 → #0A1220 (deep navy, ~95% black)
- Brush.Bg.Sidebar : #0E1218 → #0E1422
- Brush.Bg.Card    : #161B23 → #161D2C
- Brush.Bg.Footer  : #050709 → #060A14
- New Brush.Bg.BlueTint : #3050A0 @ 8% opacity, used as overlay

MainWindow.xaml
- Outer Grid Background : hardcoded "Black" → Brush.Bg.Window
  (so future tweaks of the brush propagate)
- New Rectangle on top of the body Background.png with the blue tint
  brush, IsHitTestVisible=False so it doesn't block clicks.

Versions bumped to 0.18.0.

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

src/PSLauncher.App/Views/MainWindow.xaml

@@ -192,7 +192,7 @@
         La sidebar a RowSpan=2 → s'étend du sous-topbar jusqu'au bas
         de fenêtre. Le footer est confiné à la colonne content.
     -->
-    <Grid Background="Black">
+    <Grid Background="{StaticResource Brush.Bg.Window}">
         <Grid.ColumnDefinitions>
             <ColumnDefinition Width="200" />
             <ColumnDefinition Width="*" />
@@ -216,6 +216,12 @@
                             Opacity="0.25" />
             </Rectangle.Fill>
         </Rectangle>
+        <!-- Voile bleuté (~8% opacité) posé sur l'image pour donner la teinte
+             navy/cyan d'ASTERION VR. IsHitTestVisible=False pour ne pas bloquer
+             les clics qui visent le content area. -->
+        <Rectangle Grid.Row="1" Grid.Column="1"
+                   Fill="{StaticResource Brush.Bg.BlueTint}"
+                   IsHitTestVisible="False" />
 
         <!-- Top bar : 3 colonnes (brand / license center / chrome).
              Grid.ColumnSpan=2 → s'étend sur sidebar + content. -->