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>

Pages/EditionPage.xaml

@@ -1,20 +0,0 @@
-<Page x:Class="InstaSoftOfficeTool.Pages.EditionPage"
-      xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
-      xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
-      Background="Transparent">
-
-    <Grid Margin="40,30">
-        <Grid.RowDefinitions>
-            <RowDefinition Height="Auto"/>
-            <RowDefinition Height="*"/>
-        </Grid.RowDefinitions>
-
-        <StackPanel Grid.Row="0" Margin="0,0,0,24">
-            <TextBlock x:Name="TitleText" Text="Valasszon kiadast" FontSize="24" FontWeight="Light"/>
-            <TextBlock x:Name="SubtitleText" FontSize="14"
-                       Foreground="{StaticResource TextSecondaryBrush}" Margin="0,4,0,0"/>
-        </StackPanel>
-
-        <StackPanel x:Name="EditionPanel" Grid.Row="1" VerticalAlignment="Top"/>
-    </Grid>
-</Page>