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/Company/CompanySettingsDtos.cs

@@ -112,6 +112,7 @@ namespace PowderCoating.Application.DTOs.Company
 
         // Labor Rates
         public decimal StandardLaborRate { get; set; }
+        public decimal? LaborCostPerHour { get; set; }
         public decimal AdditionalCoatLaborPercent { get; set; }
 
         // Equipment Operating Costs
@@ -185,6 +186,10 @@ namespace PowderCoating.Application.DTOs.Company
         [Display(Name = "Standard Labor Rate ($/hr)")]
         public decimal StandardLaborRate { get; set; }
 
+        [Range(0, 10000, ErrorMessage = "Labor cost rate must be between 0 and 10,000")]
+        [Display(Name = "Shop Labor Cost Rate ($/hr)")]
+        public decimal? LaborCostPerHour { get; set; }
+
         [Range(0, 100, ErrorMessage = "Additional coat labor percent must be between 0 and 100")]
         [Display(Name = "Additional Coat Labor (%)")]
         public decimal AdditionalCoatLaborPercent { get; set; } = 30m;