Add Phase B: Inventory COGS auto-posting to GL on JobUsage transactions

When powder is consumed via a job (JobsController) or scan (InventoryController.LogUsage),
debit the item's CogsAccountId and credit its InventoryAccountId for the cost of the
quantity consumed (using AverageCost if available, else UnitCost). No-op when either
GL account is not configured on the InventoryItem.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/PowderCoating.Web/Controllers/JobsController.cs

@@ -37,6 +37,7 @@ public class JobsController : Controller
     private readonly IJobItemAssemblyService _jobItemAssemblyService;
     private readonly IHubContext<NotificationHub> _hub;
     private readonly IHubContext<ShopHub> _shopHub;
+    private readonly IAccountBalanceService _accountBalanceService;
 
     public JobsController(
         IUnitOfWork unitOfWork,
@@ -52,7 +53,8 @@ public class JobsController : Controller
         IPricingCalculationService pricingService,
         IJobItemAssemblyService jobItemAssemblyService,
         IHubContext<NotificationHub> hub,
-        IHubContext<ShopHub> shopHub)
+        IHubContext<ShopHub> shopHub,
+        IAccountBalanceService accountBalanceService)
     {
         _unitOfWork = unitOfWork;
         _mapper = mapper;
@@ -68,6 +70,7 @@ public class JobsController : Controller
         _jobItemAssemblyService = jobItemAssemblyService;
         _hub = hub;
         _shopHub = shopHub;
+        _accountBalanceService = accountBalanceService;
     }
 
     /// <summary>
@@ -2726,6 +2729,14 @@ public class JobsController : Controller
                                 inventoryItem.QuantityOnHand -= deductNow;
                                 await _unitOfWork.InventoryItems.UpdateAsync(inventoryItem);
 
+                                // GL: DR COGS, CR Inventory Asset (accrual) — no-op if accounts not configured
+                                if (inventoryItem.CogsAccountId.HasValue && inventoryItem.InventoryAccountId.HasValue)
+                                {
+                                    var cost = deductNow * (inventoryItem.AverageCost > 0 ? inventoryItem.AverageCost : inventoryItem.UnitCost);
+                                    await _accountBalanceService.DebitAsync(inventoryItem.CogsAccountId, cost);
+                                    await _accountBalanceService.CreditAsync(inventoryItem.InventoryAccountId, cost);
+                                }
+
                                 _logger.LogInformation(
                                     "Deducted {Lbs} lbs (net of pre-logged) of {Item} from inventory for Job {JobNumber}. New quantity: {NewQty}",
                                     deductNow, inventoryItem.Name, job.JobNumber, inventoryItem.QuantityOnHand);