Fix log material dropdown showing undefined - camelCase JSON serialization

System.Text.Json defaults to PascalCase; JS reads camelCase. Add
JsonNamingPolicy.CamelCase to the InventoryItemsForModal serialization.

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

src/PowderCoating.Web/Controllers/JobsController.cs

@@ -503,7 +503,9 @@ public class JobsController : Controller
                 .OrderBy(i => i.Name)
                 .Select(i => new { i.Id, i.Name, i.UnitOfMeasure, i.QuantityOnHand })
                 .ToList();
-            ViewBag.InventoryItemsForModal = System.Text.Json.JsonSerializer.Serialize(inventoryItemsForModal);
+            ViewBag.InventoryItemsForModal = System.Text.Json.JsonSerializer.Serialize(
+                inventoryItemsForModal,
+                new System.Text.Json.JsonSerializerOptions { PropertyNamingPolicy = System.Text.Json.JsonNamingPolicy.CamelCase });
 
             // Pre-logged powder grouped by InventoryItemId (for Complete Job modal pre-fill)
             ViewBag.PreLoggedPowder = allJobTransactions