ci: publish only the web application container

Disable container support for tests and bump the application version to
1.2.1.

CaddyManager.Tests/CaddyManager.Tests.csproj

@@ -6,6 +6,16 @@
         <ImplicitUsings>enable</ImplicitUsings>
         <IsPackable>false</IsPackable>
         <IsTestProject>true</IsTestProject>
+        <!--
+            The test SDK makes this project an executable, so a solution wide
+            `dotnet publish /t:PublishContainer` containerizes it alongside the web app, pushes both
+            to the same repository and tag, and lets the last one to finish win. That shipped an
+            image whose entrypoint was the test assembly, which exits 0 without output, so the
+            container looked like it started and stopped for no reason.
+            The pipelines publish the web app project explicitly; this keeps a solution wide publish
+            from ever producing an image from the tests again.
+        -->
+        <EnableSdkContainerSupport>false</EnableSdkContainerSupport>
     </PropertyGroup>
 
     <ItemGroup>