feat(FN-1640): add Frontend UX Design built-in workflow template

- Add Frontend UX Design template for verifying UI/UX design implementation
- Include WCAG 2.1 compliance checks, design system adherence, and user flow validation
- Add template to WorkflowStepManager with category-based organization
- Update documentation with new template description
- Add tests for template API endpoints and workflow step manager

packages/dashboard/app/components/WorkflowStepManager.tsx

@@ -98,6 +98,8 @@ function getTemplateIcon(iconName: string | undefined) {
       return Eye;
     case "globe":
       return Globe;
+    case "layout-grid":
+      return LayoutGrid;
     default:
       return CheckCircle;
   }