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.Core/Enums/Enums.cs

@@ -78,17 +78,6 @@ public enum EquipmentStatus
     Retired = 4
 }
 
-public enum ShopWorkerRole
-{
-    GeneralLabor = 0,
-    Sandblaster = 1,
-    Coater = 2,
-    Masker = 3,
-    QualityControl = 4,
-    OvenOperator = 5,
-    Supervisor = 6,
-    Maintenance = 7
-}
 
 public enum JobPhotoType
 {