v1.19 — Bug fixes, Hungarian accents, better error handling

- Fix: Back button was always visible (ternary always returned Visible)
- Fix: Missing Hungarian accents on EditionPage ("Válasszon kiadást")
- Fix: Better ODT download error messages (network/timeout distinguished)
- Signed with Azure Trusted Signing (Microsoft root CA, instant SmartScreen trust)

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

MainWindow.xaml

@@ -45,7 +45,7 @@
                                    Foreground="{StaticResource TextSecondaryBrush}" Margin="0,-2,0,0"/>
                     </StackPanel>
                 </StackPanel>
-                <TextBlock Text="v1.17" HorizontalAlignment="Right" VerticalAlignment="Center"
+                <TextBlock Text="v1.19" HorizontalAlignment="Right" VerticalAlignment="Center"
                            FontSize="12" Foreground="{StaticResource TextSecondaryBrush}"/>
             </Grid>
         </Border>