feat(svc): IArenaTwoPickService + response DTOs + GetTopAsync

6 response DTOs, IArenaTwoPickService interface + ArenaTwoPickException,
ArenaTwoPickService skeleton with GetTopAsync implemented and stubs for
Tasks 13-15. 3 NUnit tests for GetTopAsync all pass. DI: AddScoped.

SVSim.EmulatedEntrypoint/Program.cs

@@ -105,6 +105,7 @@ public class Program
         builder.Services.AddScoped<IViewerStoryProgressRepository, ViewerStoryProgressRepository>();
         builder.Services.AddScoped<IArenaTwoPickRunRepository, ArenaTwoPickRunRepository>();
         builder.Services.AddScoped<IArenaTwoPickCardPoolService, ArenaTwoPickCardPoolService>();
+        builder.Services.AddScoped<IArenaTwoPickService, ArenaTwoPickService>();
         builder.Services.AddScoped<IStoryService, StoryService>();
         builder.Services.AddScoped<IDeckListBuilder, DeckListBuilder>();
         builder.Services.AddSingleton<IRandom, SystemRandom>();