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/Import/ShopWorkerImportDto.cs

@@ -1,28 +0,0 @@
-using CsvHelper.Configuration.Attributes;
-
-namespace PowderCoating.Application.DTOs.Import;
-
-/// <summary>
-/// DTO for importing shop workers from CSV files.
-/// Valid Role values: GeneralLabor, Sandblaster, Coater, Masker, QualityControl, OvenOperator, Supervisor, Maintenance
-/// </summary>
-public class ShopWorkerImportDto
-{
-    [Name("Name")]
-    public string Name { get; set; } = string.Empty;
-
-    [Name("Role")]
-    public string Role { get; set; } = "GeneralLabor";
-
-    [Name("Phone")]
-    public string? Phone { get; set; }
-
-    [Name("Email")]
-    public string? Email { get; set; }
-
-    [Name("IsActive")]
-    public bool? IsActive { get; set; }
-
-    [Name("Notes")]
-    public string? Notes { get; set; }
-}