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>

Pages/WelcomePage.xaml.cs

@@ -0,0 +1,31 @@
+using System.Windows;
+using System.Windows.Controls;
+
+namespace InstaSoftOfficeTool.Pages
+{
+    public partial class WelcomePage : Page
+    {
+        private readonly MainWindow _main;
+
+        public WelcomePage(MainWindow main)
+        {
+            InitializeComponent();
+            _main = main;
+        }
+
+        private void InstallClick(object sender, RoutedEventArgs e)
+        {
+            _main.StartInstallFlow();
+        }
+
+        private void RemoveClick(object sender, RoutedEventArgs e)
+        {
+            _main.StartRemoveFlow();
+        }
+
+        private void LicenseClick(object sender, RoutedEventArgs e)
+        {
+            _main.StartLicenseFlow();
+        }
+    }
+}