Add AI Catalog Price Check feature

Claude reviews every active catalog item against the shop's own operating costs
and returns a per-item verdict (below-cost / thin-margin / high / ok) with a
suggested price range, cost floor, and assumptions.

- New entity: CatalogPriceCheckReport (JSON blob, archived per company)
- New service: IAiCatalogPriceCheckService / AiCatalogPriceCheckService
  batches items 25 at a time to stay within model context limits
- Two new controller actions: GET AiPriceCheck (view report) + POST RunAiPriceCheck
- AiPriceCheck view: summary cards (counts by verdict), color-coded item cards
  with Edit Price link, assumptions detail, and loading spinner on submit
- AI Price Check button added to catalog Index header
- Migration AddCatalogPriceCheckReport applied

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

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

@@ -22,7 +22,12 @@
     <script src="~/js/catalog.js"></script>
 }
 
-<div class="d-flex justify-content-end align-items-center mb-4">
+<div class="d-flex justify-content-end align-items-center gap-2 mb-4">
+    <a asp-action="AiPriceCheck" class="btn btn-outline-primary text-nowrap">
+        <i class="bi bi-robot me-2"></i>
+        <span class="d-none d-sm-inline">AI Price Check</span>
+        <span class="d-inline d-sm-none">AI</span>
+    </a>
     <a asp-action="ExportCatalogPdf" class="btn btn-primary text-nowrap">
         <i class="bi bi-file-pdf me-2"></i>
         <span class="d-none d-sm-inline">Export Product Catalog to PDF</span>