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/DTOs/User/UserManagementDtos.cs

@@ -217,6 +217,10 @@ public class UpdateCompanyUserDto
     [Display(Name = "Active")]
     public bool IsActive { get; set; }
 
+    [Range(0, 10000, ErrorMessage = "Labor cost rate must be between 0 and 10,000")]
+    [Display(Name = "Labor Cost Rate ($/hr)")]
+    public decimal? LaborCostPerHour { get; set; }
+
     [Required(ErrorMessage = "Hire date is required")]
     [Display(Name = "Hire Date")]
     public DateTime HireDate { get; set; }