perf(host): compile inbound API methods in parallel at startup

Claude-Session: https://claude.ai/code/session_01MtdgwpEeCUn6cUA5f1LMPj

src/ZB.MOM.WW.ScadaBridge.Host/Program.cs

@@ -403,10 +403,10 @@ try
             var apiRepo = scope.ServiceProvider.GetRequiredService<ZB.MOM.WW.ScadaBridge.Commons.Interfaces.Repositories.IInboundApiRepository>();
             var executor = app.Services.GetRequiredService<ZB.MOM.WW.ScadaBridge.InboundAPI.InboundScriptExecutor>();
             var methods = await apiRepo.GetAllApiMethodsAsync();
-            foreach (var method in methods)
+            // Parallel: CompileAndRegister is safe for concurrent callers (ConcurrentDictionary
-            {
+            // caches, no shared mutable compile state); serial Roslyn compiles stretch the
-                executor.CompileAndRegister(method);
+            // failover-recovery window at hundreds of methods (arch-review PLAN-06 Task 7).
-            }
+            Parallel.ForEach(methods, method => executor.CompileAndRegister(method));
         }
 
         await app.RunAsync();