v1.07 — Pre-install Office check before installation

- New PreInstallCheckPage between Summary and Progress
- Detects existing Office installs, offers removal before new install
- License cleanup option included
- Skip button to proceed without removal
- Auto-proceeds to install after removal completes

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

MainWindow.xaml

@@ -42,7 +42,7 @@
                                    Foreground="{StaticResource TextSecondaryBrush}" Margin="0,-2,0,0"/>
                     </StackPanel>
                 </StackPanel>
-                <TextBlock Text="v1.06" HorizontalAlignment="Right" VerticalAlignment="Center"
+                <TextBlock Text="v1.07" HorizontalAlignment="Right" VerticalAlignment="Center"
                            FontSize="12" Foreground="{StaticResource TextSecondaryBrush}"/>
             </Grid>
         </Border>