content: wire Serilog into SVSim.ContentServer

Calls UseSvSimSerilog("svsim-content") right after CreateBuilder and
wraps Main in try/catch/finally. No environment gate needed —
ContentServer has no test-suite path. The existing manual request-log
middleware (uses ILogger<Program>) now flows through Serilog
automatically; swapping it for UseSerilogRequestLogging() is a
follow-up per the spec.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

SVSim.ContentServer/SVSim.ContentServer.csproj

@@ -8,4 +8,8 @@
     <RootNamespace>SVSim.ContentServer</RootNamespace>
   </PropertyGroup>
 
+  <ItemGroup>
+    <ProjectReference Include="..\SVSim.Hosting\SVSim.Hosting.csproj" />
+  </ItemGroup>
+
 </Project>