fix(build): update slnx to reference renamed FSH.Api project

Playground.Api was renamed to FSH.Api but the solution file
was not updated, causing CI build failures.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: iammukeshm

src/FSH.Framework.slnx

@@ -31,7 +31,7 @@
   </Folder>
   <Folder Name="/Playground/">
     <Project Path="Playground/FSH.Playground.AppHost/FSH.Playground.AppHost.csproj" Id="86bd02ee-f1b5-472c-b5bd-bc607fe084de" />
-    <Project Path="Playground/Playground.Api/Playground.Api.csproj" Id="187ce245-0a57-469c-96c2-a88902f2d40d" />
+    <Project Path="Playground/FSH.Api/FSH.Api.csproj" Id="187ce245-0a57-469c-96c2-a88902f2d40d" />
     <Project Path="Playground/Playground.Blazor/Playground.Blazor.csproj" />
   </Folder>
   <Folder Name="/Playground/Migrations/">
@@ -43,6 +43,7 @@
     <Project Path="Tests/Generic.Tests/Generic.Tests.csproj" />
     <Project Path="Tests/Identity.Tests/Identity.Tests.csproj" />
     <Project Path="Tests/Multitenancy.Tests/Multitenancy.Tests.csproj" Id="985345a2-edb4-4ef9-9a1b-59b704f523b6" />
+    <Project Path="Tests/Integration.Tests/Integration.Tests.csproj" />
   </Folder>
   <Folder Name="/Tools/">
     <Project Path="Tools/CLI/FSH.CLI.csproj" />