Sync: keep the remembered sign-in when the provider is merely down, and say why SYNC NOW found the machine offline

src/DodoSSH.Client.App/Views/SettingsVaultsPage.axaml

@@ -70,6 +70,13 @@
           </StackPanel>
         </Grid>
 
+        <!-- What SYNC NOW said. The status bar that carries it elsewhere is hidden in settings mode, so
+             without this the button ran, failed or found the machine offline in perfect silence. -->
+        <TextBlock Margin="0,10,0,0" FontSize="11.5" TextWrapping="Wrap" HorizontalAlignment="Right"
+                   Foreground="{StaticResource TextFaint}"
+                   IsVisible="{Binding Vault.Status, Converter={x:Static StringConverters.IsNotNullOrEmpty}, FallbackValue=False}"
+                   Text="{Binding Vault.Status}" />
+
         <!-- The name-a-vault and rename-a-vault forms, in place — this window has no modal idiom for a bare
              text field, and the members panel below is a different kind of overlay: over one vault's people,
              not over a form. -->