Fix incoming powder inventory: defer creation to approval, deduplicate, fix category

Three bugs fixed:

1. Wrong timing — inventory items with IsIncoming=true were auto-created during
   quote save (in QuotePricingAssemblyService). Now deferred to quote approval so
   inventory only reflects powders the shop is actually going to process.

2. Duplicate records — same powder on multiple items in one quote created multiple
   inventory records. Now grouped by PowderCatalogItemId: one record per unique
   catalog powder, all matching coats linked to the same record.

3. Wrong category — category resolution used first IsCoating=true by DisplayOrder,
   which could land items in Cerakote or other unintended categories. Now prefers
   CategoryCode==POWDER explicitly, with DisplayOrder fallback.

Changes:
- QuoteItemCoat: add PowderCatalogItemId int? — persists catalog reference at quote
  save time so the approval path knows what to create
- QuotePricingAssemblyService.BuildQuoteItemCoatsAsync: store PowderCatalogItemId
  on coat instead of calling CreateIncomingInventoryItemAsync immediately
- QuotePricingAssemblyService.CreateIncomingInventoryItemAsync: signature changed
  from (coatDto, companyId) to (catalogItemId, companyId); category lookup prefers
  POWDER code; no longer clears PowderCostPerLb on the DTO
- QuotePricingAssemblyService.EnsureIncomingInventoryForApprovedQuoteAsync: new
  public method called at approval — loads pending coats, groups by catalog ID,
  creates one inventory item per group, links all coats in each group
- IQuotePricingAssemblyService: exposes EnsureIncomingInventoryForApprovedQuoteAsync
- QuotesController.ApproveQuote: calls EnsureIncomingInventory after save
- QuotesController.ChangeQuoteStatus: calls EnsureIncomingInventory on Approved
- QuoteApprovalController: injects IQuotePricingAssemblyService; calls
  EnsureIncomingInventory in ApproveInternal (customer-facing portal path)
- InventoryController.CreateIncomingFromCatalog: same category fix (prefers POWDER)
- Migration: AddPowderCatalogItemIdToCoat (nullable int on QuoteItemCoats)
- Tests: updated AddAsIncoming test to verify deferred behavior; new deduplication test

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

tests/PowderCoating.UnitTests/QuoteApprovalControllerTests.cs

@@ -326,7 +326,8 @@ public class QuoteApprovalControllerTests
             Mock.Of<IStripeConnectService>(),
             Mock.Of<ILogger<QuoteApprovalController>>(),
             new ConfigurationBuilder().Build(),
-            hubContext.Object);
+            hubContext.Object,
+            Mock.Of<IQuotePricingAssemblyService>());
 
         var httpContext = new DefaultHttpContext();
         if (remoteIpAddress != null)

tests/PowderCoating.UnitTests/QuotePricingAssemblyServiceTests.cs

@@ -225,8 +225,13 @@ public class QuotePricingAssemblyServiceTests
         Assert.Equal(170m, item.TotalPrice);
     }
 
+    /// <summary>
+    /// Verifies that CreateQuoteItemsAsync does NOT create inventory during quote save.
+    /// The catalog item ID is stored on PowderCatalogItemId for later use at approval.
+    /// PowderCostPerLb is preserved (not cleared) so the Custom Powder Order item still prices correctly.
+    /// </summary>
     [Fact]
-    public async Task CreateQuoteItemsAsync_AddAsIncoming_CreatesInventoryItemAndLinksCoat()
+    public async Task CreateQuoteItemsAsync_AddAsIncoming_StoresCatalogIdWithoutCreatingInventory()
     {
         await using var context = CreateContext();
         context.Set<PowderCatalogItem>().Add(new PowderCatalogItem
@@ -288,11 +293,72 @@ public class QuotePricingAssemblyServiceTests
             ovenRateOverride: null,
             createdAtUtc: DateTime.UtcNow));
 
-        var inventoryItem = await context.InventoryItems.SingleAsync();
+        // No inventory created at quote-save time
+        Assert.Empty(await context.InventoryItems.ToListAsync());
+
+        // Coat stores the catalog item ID for deferred creation at approval
         var coat = Assert.Single(item.Coats);
-        Assert.Equal(inventoryItem.Id, coat.InventoryItemId);
-        Assert.True(inventoryItem.IsIncoming);
-        Assert.Null(dto.Coats[0].PowderCostPerLb);
+        Assert.Equal(5, coat.PowderCatalogItemId);
+        Assert.Null(coat.InventoryItemId);
+
+        // PowderCostPerLb preserved (not cleared) so Custom Powder Order item can price correctly
+        Assert.Equal(22m, dto.Coats[0].PowderCostPerLb);
+    }
+
+    /// <summary>
+    /// Verifies that EnsureIncomingInventoryForApprovedQuoteAsync creates one inventory item per
+    /// unique catalog powder, even when multiple quote items/coats reference the same catalog ID.
+    /// </summary>
+    [Fact]
+    public async Task EnsureIncomingInventory_DeduplicatesSameCatalogIdAcrossCoats()
+    {
+        await using var context = CreateContext();
+
+        // Add catalog item and a "POWDER" category
+        context.Set<PowderCatalogItem>().Add(new PowderCatalogItem
+        {
+            Id = 5,
+            VendorName = "Prismatic Powders",
+            Sku = "P-1001",
+            ColorName = "Candy Red",
+            UnitPrice = 19.5m,
+            CoverageSqFtPerLb = 85m,
+            TransferEfficiency = 70m
+        });
+        context.InventoryCategoryLookups.Add(new InventoryCategoryLookup
+        {
+            Id = 10,
+            CompanyId = 1,
+            CategoryCode = "POWDER",
+            DisplayName = "Powder",
+            DisplayOrder = 1,
+            IsActive = true,
+            IsCoating = true,
+            CreatedAt = DateTime.UtcNow
+        });
+
+        // Two coats on different QuoteItems, both referencing catalog item 5
+        var qi1 = new QuoteItem { Id = 1, QuoteId = 9, CompanyId = 1, Description = "Item A", CreatedAt = DateTime.UtcNow };
+        var qi2 = new QuoteItem { Id = 2, QuoteId = 9, CompanyId = 1, Description = "Item B", CreatedAt = DateTime.UtcNow };
+        context.QuoteItems.AddRange(qi1, qi2);
+        await context.SaveChangesAsync();
+
+        var coat1 = new QuoteItemCoat { QuoteItemId = 1, CompanyId = 1, PowderCatalogItemId = 5, CoatName = "Base", Sequence = 1, CoverageSqFtPerLb = 30, TransferEfficiency = 65, CreatedAt = DateTime.UtcNow };
+        var coat2 = new QuoteItemCoat { QuoteItemId = 2, CompanyId = 1, PowderCatalogItemId = 5, CoatName = "Base", Sequence = 1, CoverageSqFtPerLb = 30, TransferEfficiency = 65, CreatedAt = DateTime.UtcNow };
+        context.Set<QuoteItemCoat>().AddRange(coat1, coat2);
+        await context.SaveChangesAsync();
+
+        var service = CreateService(context, Mock.Of<IPricingCalculationService>());
+        await service.EnsureIncomingInventoryForApprovedQuoteAsync(quoteId: 9, companyId: 1);
+
+        // Exactly ONE inventory item should be created (not two)
+        var inventoryItems = await context.InventoryItems.ToListAsync();
+        Assert.Single(inventoryItems);
+        Assert.True(inventoryItems[0].IsIncoming);
+
+        // Both coats linked to the same inventory item
+        var updatedCoats = await context.Set<QuoteItemCoat>().ToListAsync();
+        Assert.All(updatedCoats, c => Assert.Equal(inventoryItems[0].Id, c.InventoryItemId));
     }
 
     private static QuotePricingAssemblyService CreateService(ApplicationDbContext context, IPricingCalculationService pricingService)