Fix Rollback NRE: capture filename before refreshing the checkpoint list

The actual restore on the service was succeeding but the GUI showed
"Rollback failed: Object reference not set to an instance of an object."
because RefreshAsync clears the ObservableCollection, the SelectedItem
binding goes null when its source item disappears, and the next line
dereferenced Selected!.FileName.

Cache the filename and timestamp before any await so the post-refresh
status update doesn't depend on Selected still being non-null.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Directory.Build.props

@@ -1,7 +1,7 @@
 <Project>
 
   <PropertyGroup>
-    <Version>0.1.4</Version>
+    <Version>0.1.3</Version>
     <Authors>Justin Paul</Authors>
     <Company>Justin Paul</Company>
     <Product>Webhook Server</Product>