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.Web/Controllers/DataPurgeController.cs

@@ -175,7 +175,6 @@ public class DataPurgeController : Controller
         stats.Add(await Stat("Equipment",         "Equipment",           "bi-tools",       "Inventory & Ops", _db.Equipment.Where(e => e.IsDeleted)));
         stats.Add(await Stat("MaintenanceRecords","Maintenance Records",  "bi-wrench",      "Inventory & Ops", _db.MaintenanceRecords.Where(e => e.IsDeleted)));
         stats.Add(await Stat("Vendors",           "Vendors",             "bi-truck",       "Inventory & Ops", _db.Vendors.Where(e => e.IsDeleted)));
-        stats.Add(await Stat("ShopWorkers",       "Shop Workers",        "bi-person-badge","Inventory & Ops", _db.ShopWorkers.Where(e => e.IsDeleted)));
 
         return stats;
     }
@@ -204,7 +203,6 @@ public class DataPurgeController : Controller
             "Equipment"          => await QueryCount(_db.Equipment, cutoff),
             "MaintenanceRecords" => await QueryCount(_db.MaintenanceRecords, cutoff),
             "Vendors"            => await QueryCount(_db.Vendors, cutoff),
-            "ShopWorkers"        => await QueryCount(_db.ShopWorkers, cutoff),
             _                    => (0, null)
         };
     }
@@ -324,11 +322,6 @@ public class DataPurgeController : Controller
                     .Where(e => e.IsDeleted && e.DeletedAt <= cutoff).ExecuteDeleteAsync();
                 break;
 
-            case "ShopWorkers":
-                count = await _db.ShopWorkers.IgnoreQueryFilters()
-                    .Where(e => e.IsDeleted && e.DeletedAt <= cutoff).ExecuteDeleteAsync();
-                break;
-
             default:
                 return 0;
         }