Fix QR scan stripping scheme from product URL

LookupAsync builds SpecPageUrl from the ProductUrlTemplate via TryBuildDirectUrl.
If the template is stored without a scheme the link is scheme-less and browsers
treat it as relative, appending it to the app URL.

The scanned QR URL is always fully-qualified and always the correct product page
(it came from the manufacturer's bag), so use it unconditionally as SpecPageUrl
on the pattern-matched QR path instead of only when SpecPageUrl was null.

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

src/PowderCoating.Web/Controllers/InventoryController.cs

@@ -946,7 +946,10 @@ public class InventoryController : Controller
             if (!string.IsNullOrWhiteSpace(urlMfr))
             {
                 aiResult = await _aiLookupService.LookupAsync(urlMfr, urlColor, null, urlPart);
-                if (aiResult.Success && aiResult.SpecPageUrl == null)
+                // The scanned QR URL is always the authoritative product page link — it came
+                // directly from the manufacturer's bag and is always fully-qualified. Overwrite
+                // whatever LookupAsync returned (which may be a scheme-less path from the template).
+                if (aiResult.Success)
                     aiResult.SpecPageUrl = qrUrl;
             }
             else