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.Application/Services/PricingCalculationService.cs

@@ -252,11 +252,27 @@ public class PricingCalculationService : IPricingCalculationService
             };
         }
 
-        // AI items use ManualUnitPrice directly (set to either the AI estimate or the user's price override).
-        // The AI already factored in all costs — skip the pricing engine entirely.
+        // AI items use ManualUnitPrice as the single-coat base price.
+        // Apply the same additional-coat charge as the calculated-item path so that
+        // adding a 2nd or 3rd coat in step 3 increases the price by AdditionalCoatLaborPercent%
+        // per coat — matching what catalog/calculated items charge.
         if (item.IsAiItem && item.ManualUnitPrice.HasValue)
         {
             var aiUnitPrice = item.ManualUnitPrice.Value;
+
+            int additionalAiCoats = 0;
+            if (item.Coats != null)
+            {
+                for (int i = 1; i < item.Coats.Count; i++)
+                {
+                    if (!item.Coats[i].NoExtraLayerCharge)
+                        additionalAiCoats++;
+                }
+            }
+            if (additionalAiCoats > 0)
+                aiUnitPrice = Math.Round(
+                    aiUnitPrice * (1m + additionalAiCoats * (costs.AdditionalCoatLaborPercent / 100m)), 2);
+
             var aiTotal = aiUnitPrice * item.Quantity;
             return new QuoteItemPricingResult
             {