v1.08 — Custom Fluent confirmation dialog, replace all MessageBox

- New ConfirmDialog overlay with dark backdrop, rounded card, shadow
- Warning/Question/Error icon types with accent colors
- Replaced all MessageBox.Show calls (RemovePage, PreInstallCheck, Troubleshoot)
- Click outside dialog = cancel

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

MainWindow.xaml

@@ -1,6 +1,7 @@
 <Window x:Class="InstaSoftOfficeTool.MainWindow"
         xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
         xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
+        xmlns:pages="clr-namespace:InstaSoftOfficeTool.Pages"
         Title="InstaSoft Office Tool"
         Width="800" Height="550"
         ResizeMode="NoResize"
@@ -9,6 +10,8 @@
         TextElement.Foreground="{StaticResource TextPrimaryBrush}">
 
     <Grid>
+        <!-- Main content -->
+        <Grid x:Name="MainGrid">
         <Grid.RowDefinitions>
             <RowDefinition Height="64"/>
             <RowDefinition Height="*"/>
@@ -42,7 +45,7 @@
                                    Foreground="{StaticResource TextSecondaryBrush}" Margin="0,-2,0,0"/>
                     </StackPanel>
                 </StackPanel>
-                <TextBlock Text="v1.07" HorizontalAlignment="Right" VerticalAlignment="Center"
+                <TextBlock Text="v1.08" HorizontalAlignment="Right" VerticalAlignment="Center"
                            FontSize="12" Foreground="{StaticResource TextSecondaryBrush}"/>
             </Grid>
         </Border>
@@ -70,5 +73,9 @@
                 </StackPanel>
             </Grid>
         </Border>
+        </Grid>
+
+        <!-- Confirm dialog overlay -->
+        <pages:ConfirmDialog x:Name="Dialog" Grid.RowSpan="3"/>
     </Grid>
 </Window>