Add IsIncoming inventory flag and catalog-to-incoming powder flow in item wizard

- InventoryItem.IsIncoming: marks powder ordered but not yet received; enables QR code
  printing on work orders while the shipment is in transit
- InventoryController.CreateIncomingFromCatalog: POST endpoint creates a 0-balance inventory
  record from a PowderCatalogItem and returns it in wizard-compatible shape
- item-wizard.js: custom coat tab now searches the platform powder catalog as a fallback;
  catalog results show an 'Add as Incoming Order' option; createIncomingFromCatalog POSTs
  to server and selects the new item without a page refresh
- QuoteItemCoatDto: CatalogItemId + AddAsIncoming fields so the wizard can signal server-side
  incoming-item creation during quote save
- Inventory Create/Edit/Index views: IsIncoming badge and field
- IInventoryAiLookupService: minor interface update
- Migration: AddInventoryIsIncoming

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

src/PowderCoating.Web/Views/Inventory/Index.cshtml

@@ -275,7 +275,13 @@
                                     <span class="fw-semibold">@((item.QuantityOnHand * item.UnitCost).ToString("C"))</span>
                                 </td>
                                 <td>
-                                    @if (item.IsActive)
+                                    @if (item.IsIncoming)
+                                    {
+                                        <span class="badge bg-warning bg-opacity-25 text-warning-emphasis">
+                                            <i class="bi bi-truck me-1"></i>Incoming
+                                        </span>
+                                    }
+                                    else if (item.IsActive)
                                     {
                                         <span class="badge bg-success bg-opacity-10 text-success">
                                             <i class="bi bi-check-circle me-1"></i>Active