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/appsettings.json

@@ -5,6 +5,14 @@
       "Microsoft.AspNetCore": "Warning"
     }
   },
+  "Serilog": {
+    "MinimumLevel": {
+      "Default": "Information",
+      "Override": {
+        "Microsoft.AspNetCore": "Warning"
+      }
+    }
+  },
   "AllowedHosts": "*",
   "Content": {
     "Root": ""