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.Web/wwwroot/js/inventory-catalog-lookup.js

@@ -54,6 +54,8 @@
             const params = new URLSearchParams();
             if (searchTerm) params.set('q', searchTerm);
             if (manufacturer) params.set('vendor', manufacturer);
+            const currentId = smartBtn.dataset.currentId;
+            if (currentId) params.set('currentId', currentId);
 
             const resp = await fetch(`${LOOKUP_URL}?${params}`);
             if (!resp.ok) throw new Error(`HTTP ${resp.status}`);
@@ -358,7 +360,7 @@
           <div class="modal-dialog modal-dialog-scrollable">
             <div class="modal-content">
               <div class="modal-header py-2">
-                <h6 class="modal-title"><i class="bi bi-list-ul me-2"></i>Multiple matches — pick one</h6>
+                <h6 class="modal-title"><i class="bi bi-list-ul me-2"></i>${items.length} match${items.length !== 1 ? 'es' : ''} — pick one <span class="text-muted fw-normal small">(already in inventory excluded)</span></h6>
                 <button type="button" class="btn-close" data-bs-dismiss="modal"></button>
               </div>
               <div class="modal-body p-0">