v1.15 — PowerShell edition + repo restructure

- New powershell/InstaSoftOfficeTool.ps1: single-file WPF GUI version
  - Same Fluent Design UI, no compilation needed
  - Runs on any Windows 7+ with PowerShell 5.1 (built-in)
  - Chrome won't flag .ps1 files as "rarely downloaded"
  - Auto-elevates to admin
- Moved C# source to src/ subfolder
- Updated .gitignore for nested bin/obj folders

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

App.xaml

@@ -1,14 +0,0 @@
-<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>