feat(ui): hardcode mainnet, remove network selector

Drop the mainnet/testnet/regtest ComboBox from the wizard and fix
Net to always return NetKind.Mainnet. Core profiles and CLI --net
flag are untouched; the wallet file still records the network name.

src/App/Localization/Loc.cs

@@ -75,8 +75,7 @@ public sealed class Loc
         ["wiz.data.usedefault"]   = ["Usa il percorso predefinito",                                       "Use the default path",         "Usar la ruta predeterminada",          "Utiliser le chemin par défaut",            "Usar o caminho padrão",                    "Standardpfad verwenden"],
         ["wiz.data.choose"]       = ["Scegli una cartella…",                                              "Choose a folder…",             "Elegir una carpeta…",                  "Choisir un dossier…",                      "Escolher uma pasta…",                      "Ordner wählen…"],
         ["wiz.choose.title"]      = ["Scegli il wallet da aprire",                                        "Choose the wallet to open",    "Elige el wallet a abrir",              "Choisissez le wallet à ouvrir",            "Escolha a carteira a abrir",               "Wallet zum Öffnen wählen"],
-        ["wiz.net"]               = ["Rete:",                                                             "Network:",                     "Red:",                                 "Réseau :",                                 "Rede:",                                    "Netzwerk:"],
-        ["wiz.open.btn"]          = ["Apri il wallet esistente",                                          "Open existing wallet",         "Abrir wallet existente",               "Ouvrir le wallet existant",                "Abrir carteira existente",                 "Vorhandenes Wallet öffnen"],
+["wiz.open.btn"]          = ["Apri il wallet esistente",                                          "Open existing wallet",         "Abrir wallet existente",               "Ouvrir le wallet existant",                "Abrir carteira existente",                 "Vorhandenes Wallet öffnen"],
         ["wiz.new.btn"]           = ["Crea un nuovo wallet",                                              "Create a new wallet",          "Crear nuevo wallet",                   "Créer un nouveau wallet",                  "Criar nova carteira",                      "Neues Wallet erstellen"],
         ["wiz.restore.btn"]       = ["Ripristina da seed",                                                "Restore from seed",            "Restaurar desde semilla",              "Restaurer depuis la graine",               "Restaurar da semente",                     "Aus Seed wiederherstellen"],
         ["wiz.open.title"]        = ["Apri il wallet",                                                    "Open the wallet",              "Abrir el wallet",                      "Ouvrir le wallet",                         "Abrir a carteira",                         "Wallet öffnen"],

src/App/ViewModels/MainWindowViewModel.Wizard.cs

@@ -341,7 +341,6 @@ public partial class MainWindowViewModel
         _walletLock?.Dispose();
         _walletLock = walletLock;
 
-        SelectedNetwork = doc.Network;
         _doc = doc;
         _account = account;
         _walletPath = path;

src/App/ViewModels/MainWindowViewModel.cs

@@ -101,13 +101,6 @@ public partial class MainWindowViewModel : ViewModelBase
 
     // ---- stato pannelli ----
 
-    public string[] Networks { get; } = ["mainnet", "testnet", "regtest"];
-
-    [ObservableProperty]
-    private string selectedNetwork = "mainnet";
-
-    partial void OnSelectedNetworkChanged(string value) => RefreshSetupState();
-
     [ObservableProperty]
     [NotifyPropertyChangedFor(nameof(IsSetupVisible))]
     private bool isWalletOpen;
@@ -130,7 +123,7 @@ public partial class MainWindowViewModel : ViewModelBase
 
     // ---- helpers ----
 
-    private NetKind Net => System.Enum.Parse<NetKind>(SelectedNetwork, ignoreCase: true);
+    private NetKind Net => NetKind.Mainnet;
     private ChainProfile Profile => ChainProfiles.For(Net);
     private ServerRegistry Registry => new(Profile, AppPaths.ServersPath(Net));
 

src/App/Views/MainView.axaml

@@ -64,11 +64,6 @@
 
                 <!-- Passo 1: scelta iniziale -->
                 <StackPanel IsVisible="{Binding IsStepStart}" Spacing="12">
-                    <StackPanel Orientation="Horizontal" Spacing="10" HorizontalAlignment="Center">
-                        <TextBlock Text="{Binding Loc[wiz.net]}" VerticalAlignment="Center"/>
-                        <ComboBox ItemsSource="{Binding Networks}"
-                                  SelectedItem="{Binding SelectedNetwork}" MinWidth="140"/>
-                    </StackPanel>
                     <Button Content="{Binding Loc[wiz.open.btn]}" FontSize="16"
                             HorizontalAlignment="Stretch" HorizontalContentAlignment="Center"
                             IsVisible="{Binding WalletFileExists}"