Remove ShopWorker entity and migrate worker identity to ApplicationUser

Removes the ShopWorker and ShopWorkerRoleCost entities, all related DTOs,
mappings, controllers, views, and import/export paths. Worker identity is
now handled entirely through ApplicationUser with per-user LaborCostPerHour.
ShopWorkerRoleCosts table remains in production pending manual data migration.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Application/Mappings/JobProfile.cs

@@ -73,7 +73,7 @@ public class JobProfile : Profile
         // JobTimeEntry → JobTimeEntryDto
         CreateMap<JobTimeEntry, JobTimeEntryDto>()
             .ForMember(dest => dest.WorkerName, opt => opt.MapFrom(src =>
-                src.UserDisplayName ?? (src.Worker != null ? src.Worker.Name : string.Empty)));
+                src.UserDisplayName ?? string.Empty));
 
         // CreateJobDto to Job
         CreateMap<CreateJobDto, Job>()