Add event-driven state sync with ETag optimization

Program.cs

@@ -46,6 +46,7 @@ builder.Services.AddScoped<AdminWorkflowService>();
 builder.Services.AddScoped<ResultsWorkflowService>();
 builder.Services.AddScoped<StateWorkflowService>();
 builder.Services.AddSingleton<AuthAttemptMonitor>();
+builder.Services.AddSingleton<StateChangeNotifier>();
 
 builder.Services.ConfigureHttpJsonOptions(options => { options.SerializerOptions.Converters.Add(new JsonStringEnumConverter()); });
 
@@ -152,6 +153,7 @@ app.UseGlobalExceptionLogging();
 app.UseAuthentication();
 app.UseMiddleware<EnsurePlayerExistsMiddleware>();
 app.UseAuthorization();
+app.UseMiddleware<StateChangeNotificationMiddleware>();
 
 app.UseDefaultFiles();
 app.UseStaticFiles();