feat(ui): persist last server and split connection status text

- AppConfig stores LastServerHost/Port/UseSsl; restored on next launch
  so the wallet reconnects to the last-used server instead of defaulting
  to the first bootstrap entry
- Added ConnectionStatusShort for the status bar (short label only);
  ConnectionStatus retains the full "Connesso a ip:porta" shown in the
  server settings overlay

src/App/Views/MainView.axaml

@@ -895,7 +895,7 @@
                              IsVisible="{Binding IsConnected}"/>
                     <Ellipse Width="10" Height="10" Fill="{DynamicResource DangerBrush}" VerticalAlignment="Center"
                              IsVisible="{Binding !IsConnected}"/>
-                    <TextBlock Text="{Binding ConnectionStatus}" FontSize="12"
+                    <TextBlock Text="{Binding ConnectionStatusShort}" FontSize="12"
                                Foreground="{DynamicResource SystemAccentColor}"
                                VerticalAlignment="Center"/>
                 </StackPanel>