fix(secrets): ${secret:} expander skips comment keys (_-prefixed leaf) — 0.1.2

Live HistorianGateway boot caught that the expander scanned a '_secretsComment' appsettings
value documenting the ${secret:...} syntax, tried to resolve the literal example token, and
crashed boot. The family uses _*Comment keys pervasively, so skip any config key whose leaf
segment starts with '_' (the _comment convention). Functional keys never lead with '_'.

ZB.MOM.WW.Secrets/Directory.Build.props

@@ -5,7 +5,7 @@
     <Nullable>enable</Nullable>
     <ImplicitUsings>enable</ImplicitUsings>
     <LangVersion>latest</LangVersion>
-    <Version>0.1.1</Version>
+    <Version>0.1.2</Version>
     <ManagePackageVersionsCentrally>true</ManagePackageVersionsCentrally>
     <PackageReadmeFile>README.md</PackageReadmeFile>
   </PropertyGroup>