fix: add missing description prop to Spinner in FieldsCard

The Spinner component requires a `description` or `aria-label` prop for
accessibility. The missing prop caused a TypeScript build failure in the
UI Docker container.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: antoniomtz

src/ui/components/FieldsCard.tsx

@@ -104,7 +104,7 @@ function FaqTabContent({ faqs, isLoading }: { faqs?: FAQ[]; isLoading?: boolean
     return (
       <div style={{ padding: '40px', textAlign: 'center' }}>
         <Stack gap="4" align="center">
-          <Spinner size="large" />
+          <Spinner size="large" description="Generating FAQs..." />
           <Text kind="body/regular/md" className="text-secondary">
             Generating FAQs...
           </Text>