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>

Pages/EditionPage.xaml.cs

@@ -17,7 +17,7 @@ namespace InstaSoftOfficeTool.Pages
             _config = config;
             _editions = OfficeEdition.GetEditions(_config.Version);
 
-            SubtitleText.Text = _config.GetVersionDisplayName() + " — melyik kiadast szeretne?";
+            SubtitleText.Text = _config.GetVersionDisplayName() + " \u2014 melyik kiad\u00e1st szeretn\u00e9?";
 
             BuildEditionCards();
         }