fix(ui): hide error banner for non-failed job statuses

job.error persists after retry succeeds — only show it when status is
tts_failed / render_failed / processing_failed.

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

frontend/src/routes/jobs/JobDetail.tsx

@@ -699,7 +699,7 @@ export function JobDetail() {
           )}
 
           {/* Error Display */}
-          {job.error && (
+          {job.error && isFailedStatus && (
             <div className="bg-red-50 border border-red-200 rounded-lg p-4">
               <div className="flex items-start gap-2 mb-2">
                 <svg className="w-5 h-5 text-red-600 flex-shrink-0 mt-0.5" fill="none" stroke="currentColor" viewBox="0 0 24 24">