Show current catalog price and price-change nudge on inventory detail

Surfaces the synced CatalogReferencePrice on the inventory detail pricing card:
"Current Catalog Price" (the price quotes use), with an info popover clarifying
it doesn't affect Unit Cost or stock value, an "Updated <date>" line, and a
badge nudging when it differs from what they last paid ("Price up/down from
$X last paid"). Adds CatalogReferencePrice/CatalogPriceUpdatedAt to
InventoryItemDto (auto-mapped). Display only — no pricing/accounting impact.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/PowderCoating.Application/DTOs/Inventory/InventoryDtos.cs

@@ -37,6 +37,8 @@ public class InventoryItemDto
     public decimal AverageCost { get; set; }
     public decimal LastPurchasePrice { get; set; }
     public DateTime? LastPurchaseDate { get; set; }
+    public decimal? CatalogReferencePrice { get; set; }
+    public DateTime? CatalogPriceUpdatedAt { get; set; }
     public int? PrimaryVendorId { get; set; }
     public string? PrimaryVendorName { get; set; }
     public string? VendorPartNumber { get; set; }

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

@@ -431,6 +431,41 @@
                                 <label class="text-muted small mb-1">Total Stock Value</label>
                                 <p class="fw-semibold text-primary mb-0 fs-5">@((Model.QuantityOnHand * Model.UnitCost).ToString("C"))</p>
                             </div>
+                            @if (Model.CatalogReferencePrice.HasValue && Model.CatalogReferencePrice.Value > 0)
+                            {
+                                <div class="col-12"><hr class="my-2" /></div>
+                                <div class="col-12">
+                                    <label class="text-muted small mb-1">
+                                        Current Catalog Price
+                                        <i class="bi bi-info-circle ms-1" role="button" tabindex="0"
+                                           data-bs-toggle="popover" data-bs-trigger="hover focus" data-bs-placement="top"
+                                           data-bs-content="The current list price from the linked manufacturer catalog, refreshed by sync. New quotes use this price. It does not change your Unit Cost or stock value."></i>
+                                    </label>
+                                    <p class="fw-semibold text-success mb-0 fs-5">
+                                        @Model.CatalogReferencePrice.Value.ToString("C")
+                                        <span class="text-muted fs-6 fw-normal">/ @Model.UnitOfMeasure</span>
+                                    </p>
+                                    @{
+                                        var catRef = Model.CatalogReferencePrice.Value;
+                                        var paidPrice = (Model.LastPurchaseDate.HasValue && Model.LastPurchasePrice > 0)
+                                            ? Model.LastPurchasePrice : Model.UnitCost;
+                                    }
+                                    @if (paidPrice > 0 && Math.Abs(catRef - paidPrice) >= 0.01m)
+                                    {
+                                        var priceUp = catRef > paidPrice;
+                                        <div class="mt-1">
+                                            <span class="badge @(priceUp ? "bg-warning text-dark" : "bg-info text-dark")">
+                                                <i class="bi @(priceUp ? "bi-arrow-up-right" : "bi-arrow-down-right") me-1"></i>
+                                                Price @(priceUp ? "up" : "down") from @paidPrice.ToString("C") last paid
+                                            </span>
+                                        </div>
+                                    }
+                                    @if (Model.CatalogPriceUpdatedAt.HasValue)
+                                    {
+                                        <div class="text-muted small mt-1">Updated @Model.CatalogPriceUpdatedAt.Value.ToLocalTime().ToString("MMM d, yyyy")</div>
+                                    }
+                                </div>
+                            }
                             @if (Model.LastPurchaseDate.HasValue)
                             {
                                 <div class="col-6">