feat(app): version in window title and Help overlay

- csproj: add <Version>0.9.0</Version> as single source of truth
- AppVersion reads Major.Minor.Build from the assembly; WindowTitle
  exposes "Palladium Wallet 0.9.0" bound to Window.Title
- Menu Help → in-app overlay (same pattern as settings/server overlays)
  showing app name, version and a short description; backdrop tap and
  Esc close it
- i18n: menu.help, help.title, help.info in all 6 languages

src/App/Localization/Loc.cs

@@ -51,6 +51,15 @@ public sealed class Loc
         ["menu.net.discover"]     = ["Cerca altri server (peer)",                                         "Discover servers (peers)",     "Buscar otros servidores (peers)",      "Rechercher d'autres serveurs (pairs)",     "Procurar outros servidores (peers)",        "Weitere Server suchen (Peers)"],
         ["menu.net.resetcerts"]   = ["Reset certificati SSL",                                             "Reset SSL certificates",       "Restablecer certificados SSL",         "Réinitialiser les certificats SSL",        "Redefinir certificados SSL",               "SSL-Zertifikate zurücksetzen"],
         ["menu.settings"]         = ["_Impostazioni",                                                     "_Settings",                    "_Configuración",                       "_Paramètres",                              "_Configurações",                           "_Einstellungen"],
+        ["menu.help"]             = ["_Help",                                                             "_Help",                        "_Ayuda",                               "_Aide",                                    "_Ajuda",                                   "_Hilfe"],
+        ["help.title"]            = ["Informazioni sul software",                                         "About this software",          "Información del software",             "À propos du logiciel",                     "Sobre o software",                         "Über die Software"],
+        ["help.info"]             = [
+            "Wallet SPV per la criptovaluta Palladium (PLM).",
+            "SPV wallet for the Palladium (PLM) cryptocurrency.",
+            "Monedero SPV para la criptomoneda Palladium (PLM).",
+            "Portefeuille SPV pour la cryptomonnaie Palladium (PLM).",
+            "Carteira SPV para a criptomoeda Palladium (PLM).",
+            "SPV-Wallet für die Kryptowährung Palladium (PLM)."],
         ["settings.unit.short"]   = ["Unità",                                                             "Unit",                         "Unidad",                               "Unité",                                    "Unidade",                                  "Einheit"],
 
         // Wizard

src/App/PalladiumWallet.App.csproj

@@ -2,6 +2,9 @@
   <PropertyGroup>
     <OutputType>WinExe</OutputType>
     <TargetFramework>net8.0</TargetFramework>
+    <!-- Versione dell'applicazione: unico punto da modificare. Compare nel
+         titolo della finestra ed è incisa nei binari pubblicati. -->
+    <Version>0.9.0</Version>
     <Nullable>enable</Nullable>
     <ApplicationManifest>app.manifest</ApplicationManifest>
     <ApplicationIcon>Assets\logo.ico</ApplicationIcon>

src/App/ViewModels/MainWindowViewModel.cs

@@ -73,6 +73,15 @@ public partial class MainWindowViewModel : ViewModelBase
     private Loc _loc = Loc.Instance;
     public Loc Loc => _loc;
 
+    /// <summary>Versione dell'app (da &lt;Version&gt; nel csproj), formato Major.Minor.Patch.</summary>
+    public static string AppVersion =>
+        typeof(MainWindowViewModel).Assembly.GetName().Version is { } v
+            ? $"{v.Major}.{v.Minor}.{v.Build}"
+            : "";
+
+    /// <summary>Titolo della finestra con la versione, es. "Palladium Wallet 0.9.0".</summary>
+    public string WindowTitle => $"Palladium Wallet {AppVersion}";
+
     /// <summary>Unità corrente per il campo importo del pannello Invia.</summary>
     public string UnitLabel => _config.Unit;
 
@@ -309,6 +318,16 @@ public partial class MainWindowViewModel : ViewModelBase
     [RelayCommand]
     private void CloseSettings() => IsSettingsOpen = false;
 
+    /// <summary>Overlay informazioni sul software (menu Help).</summary>
+    [ObservableProperty]
+    private bool isHelpOpen;
+
+    [RelayCommand]
+    private void OpenHelp() => IsHelpOpen = true;
+
+    [RelayCommand]
+    private void CloseHelp() => IsHelpOpen = false;
+
     [ObservableProperty]
     private string connectionStatus = Loc.Tr("conn.none");
 

src/App/Views/MainWindow.axaml

@@ -9,7 +9,7 @@
         x:DataType="vm:MainWindowViewModel"
         Icon="/Assets/logo.ico"
         Width="900" Height="620"
-        Title="Palladium Wallet">
+        Title="{Binding WindowTitle}">
 
     <Design.DataContext>
         <vm:MainWindowViewModel/>
@@ -28,6 +28,8 @@
             </MenuItem>
             <MenuItem Header="{Binding Loc[menu.settings]}"
                       Command="{Binding OpenSettingsCommand}"/>
+            <MenuItem Header="{Binding Loc[menu.help]}"
+                      Command="{Binding OpenHelpCommand}"/>
         </Menu>
 
         <!-- ============ WIZARD DI SETUP (§15): un passo alla volta ============ -->
@@ -714,5 +716,33 @@
                 </StackPanel>
             </Border>
         </Border>
+
+        <!-- ============ OVERLAY HELP / INFORMAZIONI ============ -->
+        <!-- Stesso pattern dell'overlay impostazioni: apertura/chiusura istantanee. -->
+        <Border Grid.Row="0" Grid.RowSpan="3"
+                Background="#99000000"
+                Tapped="OnHelpOverlayBackdropTapped"
+                IsVisible="{Binding IsHelpOpen}">
+            <Border Background="{DynamicResource SystemControlBackgroundChromeMediumLowBrush}"
+                    BorderBrush="Gray" BorderThickness="1" CornerRadius="8"
+                    Width="460"
+                    HorizontalAlignment="Center" VerticalAlignment="Center">
+                <StackPanel Margin="24" Spacing="16">
+                    <TextBlock Text="{Binding Loc[help.title]}"
+                               FontSize="18" FontWeight="Bold"/>
+
+                    <StackPanel Spacing="4">
+                        <TextBlock Text="Palladium Wallet" FontSize="16" FontWeight="Bold"/>
+                        <TextBlock Text="{Binding WindowTitle}" FontSize="12" Foreground="Gray"/>
+                    </StackPanel>
+
+                    <TextBlock Text="{Binding Loc[help.info]}" TextWrapping="Wrap"/>
+
+                    <Button Content="{Binding Loc[addr.close]}"
+                            HorizontalAlignment="Right"
+                            Command="{Binding CloseHelpCommand}"/>
+                </StackPanel>
+            </Border>
+        </Border>
     </Grid>
 </Window>

src/App/Views/MainWindow.axaml.cs

@@ -128,6 +128,13 @@ public partial class MainWindow : Window
             vm.IsSettingsOpen = false;
     }
 
+    private void OnHelpOverlayBackdropTapped(object? sender, TappedEventArgs e)
+    {
+        if (!ReferenceEquals(e.Source, sender)) return;
+        if (DataContext is MainWindowViewModel vm)
+            vm.IsHelpOpen = false;
+    }
+
     protected override void OnKeyDown(KeyEventArgs e)
     {
         if (e.Key == Key.Escape && DataContext is MainWindowViewModel vm)
@@ -136,6 +143,7 @@ public partial class MainWindow : Window
             if (vm.AddressInfo is not null) { vm.AddressInfo = null; e.Handled = true; return; }
             if (vm.IsServerSettingsOpen) { vm.IsServerSettingsOpen = false; e.Handled = true; return; }
             if (vm.IsSettingsOpen) { vm.IsSettingsOpen = false; e.Handled = true; return; }
+            if (vm.IsHelpOpen) { vm.IsHelpOpen = false; e.Handled = true; return; }
         }
         base.OnKeyDown(e);
     }