feat(ui): add user guide button to help overlay

Adds a "User guide" button next to "Report a bug" in the Help > Info
tab, linking to USERGUIDE.md on GitHub via the same Launcher pattern
used for bug reports and release pages.

src/App/Localization/Loc.cs

@@ -63,6 +63,7 @@ public sealed class Loc
         ["help.tab.info"]         = ["Info",                                                               "Info",                         "Info",                                 "Info",                                     "Info",                                     "Info"],
         ["help.tab.donate"]       = ["Dona",                                                               "Donate",                       "Donar",                                "Faire un don",                             "Doar",                                     "Spenden"],
         ["help.bug.report"]       = ["Segnala un bug",                                                     "Report a bug",                 "Informar un error",                    "Signaler un bug",                          "Reportar um bug",                          "Fehler melden"],
+        ["help.user.guide"]       = ["Guida utente",                                                       "User guide",                   "Guía del usuario",                     "Guide utilisateur",                        "Guia do usuário",                          "Benutzerhandbuch"],
         ["update.title"]          = ["Aggiornamento disponibile",                                          "Update available",             "Actualización disponible",             "Mise à jour disponible",                   "Atualização disponível",                   "Update verfügbar"],
         ["update.message"]        = ["È disponibile una nuova versione:",                                  "A new version is available:",  "Hay una nueva versión disponible:",    "Une nouvelle version est disponible :",    "Uma nova versão está disponível:",         "Eine neue Version ist verfügbar:"],
         ["update.download"]       = ["Scarica",                                                            "Download",                     "Descargar",                            "Télécharger",                              "Baixar",                                   "Herunterladen"],

src/App/Views/MainView.axaml

@@ -1563,9 +1563,14 @@
                                                    Foreground="{DynamicResource TextSecondaryBrush}"/>
                                     </StackPanel>
                                     <TextBlock Text="{Binding Loc[help.info]}" TextWrapping="Wrap"/>
+                                    <StackPanel Orientation="Horizontal" Spacing="8">
                                         <Button Content="{Binding Loc[help.bug.report]}"
                                                 Click="OnOpenBugReportClick"
                                                 HorizontalAlignment="Left"/>
+                                        <Button Content="{Binding Loc[help.user.guide]}"
+                                                Click="OnOpenUserGuideClick"
+                                                HorizontalAlignment="Left"/>
+                                    </StackPanel>
                                     <Border BorderBrush="{DynamicResource BorderSubtleBrush}"
                                             BorderThickness="0,1,0,0" Margin="0,4,0,0"/>
                                     <StackPanel Spacing="4">

src/App/Views/MainView.axaml.cs

@@ -144,6 +144,14 @@ public partial class MainView : UserControl
             await launcher.LaunchUriAsync(new Uri(issueUrl));
     }
 
+    private async void OnOpenUserGuideClick(object? sender, RoutedEventArgs e)
+    {
+        const string userGuideUrl = "https://github.com/davide3011/PalladiumWallet/blob/main/USERGUIDE.md";
+        var launcher = TopLevel.GetTopLevel(this)?.Launcher;
+        if (launcher is not null)
+            await launcher.LaunchUriAsync(new Uri(userGuideUrl));
+    }
+
     private async void OnOpenReleasePageClick(object? sender, RoutedEventArgs e)
     {
         if (DataContext is not MainWindowViewModel vm || string.IsNullOrEmpty(vm.UpdateReleaseUrl)) return;