v1.16 — Remove PowerShell edition, restore flat project structure

PowerShell version removed — will use OV code signing certificate instead.
Files moved back from src/ to project root.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

App.xaml.cs

@@ -0,0 +1,8 @@
+using System.Windows;
+
+namespace InstaSoftOfficeTool
+{
+    public partial class App : Application
+    {
+    }
+}