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/Program.cs

@@ -200,6 +200,7 @@ builder.Services.AddSingleton<IAiUsageLogger, AiUsageLogger>();
 builder.Services.AddScoped<IAiSchedulingService, AiSchedulingService>();
 builder.Services.AddScoped<IAccountingAiService, AccountingAiService>();
 builder.Services.AddScoped<IAiHelpService, AiHelpService>();
+builder.Services.AddScoped<IAiCatalogPriceCheckService, AiCatalogPriceCheckService>();
 builder.Services.AddScoped<IInventoryAiLookupService, InventoryAiLookupService>();
 builder.Services.AddHttpClient();
 builder.Services.AddScoped<ICompanyLogoService, CompanyLogoService>();