feat: make authored actions idempotent (#185)

frontend/index.html

@@ -598,7 +598,7 @@ textarea { resize: vertical; min-height: 120px; }
     if (!response.ok) throw new Error(payload.error || 'Review request failed.');
     return payload;
   }
-  const reviewController = createReviewController({ fetchJson: fetchReviewJson });
+  const reviewController = createReviewController({ fetchJson: fetchReviewJson, storage: localStorage });
   const issueController = createIssueSheet({ fetchJson: fetchReviewJson, storage: localStorage });
   const issueCapture = createIssueCapture({ fetchJson: fetchReviewJson, storage: localStorage });
   const pullController = createPullSheet({ fetchJson: fetchReviewJson, storage: localStorage });
@@ -670,10 +670,13 @@ textarea { resize: vertical; min-height: 120px; }
     return payload;
   }
 
-  async function postNotificationReply(notificationId, body) {
+  async function postNotificationReply(notificationId, body, operationId) {
     const response = await fetch('api/v1/notifications/' + encodeURIComponent(notificationId) + '/reply', {
       method: 'POST',
-      headers: { Accept: 'application/json', 'Content-Type': 'application/json' },
+      headers: {
+        Accept: 'application/json', 'Content-Type': 'application/json',
+        'Idempotency-Key': operationId,
+      },
       body: JSON.stringify({ body }),
     });
     const payload = await response.json().catch(() => ({}));