Add PWA manifest, fix AI multi-coat pricing, and improve catalog lookup

- PWA: manifest.json + minimal service worker so iOS/Android persist camera
  permission after "Add to Home Screen"; theme-color and apple meta tags in layout
- PWA icons: 192x192 and 512x512 from transparent PCL logo; updated pcl-logo.png
- AI pricing: apply AdditionalCoatLaborPercent per extra coat on AI items,
  matching the calculated-item path (was ignoring extra coats entirely)
- AI wizard: live price recalc when coats are added/removed; session-expiry
  errors now show a clear "refresh and sign in" message instead of raw HTTP status;
  smooth-scroll to follow-up/results sections on AI response
- Catalog lookup: exclude SKUs already in company inventory from results;
  pass currentId on edit so own entry still appears; vendor-scoped search
  with cross-vendor fallback; result count shown in multi-match modal

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

src/PowderCoating.Infrastructure/Services/AiQuoteService.cs

@@ -540,6 +540,16 @@ Respond with the JSON object only.";
         var complexityCharge = subtotalBeforeComplexity * complexityPct;
         var subtotal = subtotalBeforeComplexity + complexityCharge;
 
+        // Additional coat charge — each coat beyond the first adds AdditionalCoatLaborPercent % of
+        // the subtotal, matching the formula in PricingCalculationService.CalculateQuoteItemPriceAsync.
+        // The coat count here comes from the wizard's step-2 field (aiCoatCount), so the preview
+        // reflects whatever multi-coat configuration the user specified before clicking Analyze.
+        if (request.CoatCount > 1)
+        {
+            var additionalCoatCharge = subtotal * (request.CoatCount - 1) * (costs.AdditionalCoatLaborPercent / 100m);
+            subtotal += additionalCoatCharge;
+        }
+
         var markupAmount = (materialCost + consumablesSurcharge) * (costs.GeneralMarkupPercentage / 100m);
 
         // Apply shop minimum