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

@@ -0,0 +1,14 @@
+<Application x:Class="InstaSoftOfficeTool.App"
+             xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
+             xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+             StartupUri="MainWindow.xaml">
+    <Application.Resources>
+        <ResourceDictionary>
+            <ResourceDictionary.MergedDictionaries>
+                <ResourceDictionary Source="Styles/FluentTheme.xaml"/>
+                <ResourceDictionary Source="Styles/ButtonStyles.xaml"/>
+                <ResourceDictionary Source="Styles/ControlStyles.xaml"/>
+            </ResourceDictionary.MergedDictionaries>
+        </ResourceDictionary>
+    </Application.Resources>
+</Application>