feat(app): server settings as in-app overlay, split host/port fields

- Moves server configuration from the wallet panel into an overlay
  (Impostazioni → Server), same pattern as the address detail overlay
- Splits the single "host:port" text box into separate Host and Port
  fields; port changes auto-toggle the TLS checkbox when the typed
  port matches a known SSL/TCP port, and vice-versa
- Adds DisconnectAsync() so changing server/TLS reconnects to the new
  endpoint instead of reusing the old socket
- Adds i18n keys (IT/EN/ES/FR/PT/DE) for the new overlay
- Removes the server row from the main wallet panel; connection status
  indicator (green/red dot) is now shown in the wallet header

src/App/Views/MainWindow.axaml.cs

@@ -65,13 +65,19 @@ public partial class MainWindow : Window
             vm.AddressInfo = null;
     }
 
+    private void OnServerOverlayBackdropTapped(object? sender, TappedEventArgs e)
+    {
+        if (!ReferenceEquals(e.Source, sender)) return;
+        if (DataContext is MainWindowViewModel vm)
+            vm.IsServerSettingsOpen = false;
+    }
+
     protected override void OnKeyDown(KeyEventArgs e)
     {
-        if (e.Key == Key.Escape && DataContext is MainWindowViewModel { AddressInfo: not null } vm)
+        if (e.Key == Key.Escape && DataContext is MainWindowViewModel vm)
         {
-            vm.AddressInfo = null;
-            e.Handled = true;
-            return;
+            if (vm.AddressInfo is not null) { vm.AddressInfo = null; e.Handled = true; return; }
+            if (vm.IsServerSettingsOpen) { vm.IsServerSettingsOpen = false; e.Handled = true; return; }
         }
         base.OnKeyDown(e);
     }