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/PSLauncher.App.csproj

@@ -15,9 +15,9 @@
     <Product>PROSERVE Launcher</Product>
     <Copyright>© 2026 ASTERION VR — All rights reserved</Copyright>
     <RootNamespace>PSLauncher.App</RootNamespace>
-    <Version>0.17.0</Version>
-    <AssemblyVersion>0.17.0.0</AssemblyVersion>
-    <FileVersion>0.17.0.0</FileVersion>
+    <Version>0.18.0</Version>
+    <AssemblyVersion>0.18.0.0</AssemblyVersion>
+    <FileVersion>0.18.0.0</FileVersion>
 
     <!-- Single-file self-contained publish profile (used by `dotnet publish`) -->
     <PublishSingleFile>true</PublishSingleFile>