Add Office 2016 support, bump to v1.20

Office 2016 Standard, Professional Plus, and Home & Business editions
added with PerpetualVL2019 channel for volume licenses.

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

Pages/VersionPage.xaml

@@ -42,6 +42,15 @@
                                FontSize="12" Foreground="{StaticResource TextSecondaryBrush}" Margin="0,2,0,0"/>
                 </StackPanel>
             </RadioButton>
+
+            <RadioButton x:Name="Rb2016" Style="{StaticResource CardRadioButton}"
+                         GroupName="Version" Margin="0,0,0,10">
+                <StackPanel Margin="8,2">
+                    <TextBlock Text="Office 2016" FontSize="18" FontWeight="SemiBold"/>
+                    <TextBlock Text="2016. szeptemberi kiadás · Windows 7 / 8.1 / 10 · Támogatás lejárt: 2025.10."
+                               FontSize="12" Foreground="{StaticResource TextSecondaryBrush}" Margin="0,2,0,0"/>
+                </StackPanel>
+            </RadioButton>
         </StackPanel>
     </Grid>
 </Page>