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.Infrastructure/Repositories/JobRepository.cs

@@ -171,7 +171,6 @@ public class JobRepository : Repository<Job>, IJobRepository
             .Include(j => j.JobItems.Where(i => !i.IsDeleted))
                 .ThenInclude(i => i.Coats.Where(c => !c.IsDeleted))
             .Include(j => j.TimeEntries.Where(t => !t.IsDeleted))
-                .ThenInclude(t => t.Worker)
             .AsNoTracking()
             .FirstOrDefaultAsync();
     }