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/manifest.json

@@ -0,0 +1,24 @@
+{
+  "name": "Powder Coating Logix",
+  "short_name": "PCLogix",
+  "description": "Powder coating shop management — jobs, quotes, inventory, and scheduling.",
+  "start_url": "/",
+  "display": "standalone",
+  "background_color": "#ffffff",
+  "theme_color": "#1A1A1C",
+  "orientation": "any",
+  "icons": [
+    {
+      "src": "/images/pwa-icon-192.png",
+      "sizes": "192x192",
+      "type": "image/png",
+      "purpose": "any maskable"
+    },
+    {
+      "src": "/images/pwa-icon-512.png",
+      "sizes": "512x512",
+      "type": "image/png",
+      "purpose": "any maskable"
+    }
+  ]
+}