feat: retry failed extractions button on pipeline page

- POST /api/ops/pipeline/retry-failed endpoint resets extraction_failed
  docs to parsed, deletes failed intelligence rows, and re-enqueues
  them (batch of 200)
- Scheduler now auto-retries extraction_failed docs every ~10 minutes
  (100 per cycle, 60-min cooldown per doc)
- Pipeline page shows 'Retry Failed (N)' button when extraction_failed
  count > 0, with pending/success/error states

frontend/src/api/hooks.ts

@@ -525,6 +525,14 @@ export function usePipelineHealth(hours = 24) {
   return useGet<Record<string, unknown>>(['pipeline-health', hours], 'query', `/api/ops/pipeline/health?hours=${hours}`);
 }
 
+export function useRetryFailedExtractions() {
+  const qc = useQueryClient();
+  return useMutation({
+    mutationFn: () => apiPost<{ retried: number; message: string }>('query', '/api/ops/pipeline/retry-failed', {}),
+    onSuccess: () => qc.invalidateQueries({ queryKey: ['pipeline-health'] }),
+  });
+}
+
 export function useIngestionSummary(hours = 24) {
   return useGet<Record<string, unknown>>(['ingestion-summary', hours], 'query', `/api/ops/ingestion/summary?hours=${hours}`);
 }