docs(receipts): clarify receipt persistence ownership

Author: William Kempster

content/build/upload/receipts.mdx

@@ -41,6 +41,12 @@ Turbo receipts are created in three common contexts:
 
 Regardless of flow, store receipt timestamps and your own sequence metadata so ordered events can be reconstructed later.
 
+<Callout type="warning">
+  Turbo does not store and retrieve your receipts for you. If you need receipts
+  later, persist the exact payload returned by Turbo in your own storage. You
+  can also optionally store receipt records on Arweave for long-term archival.
+</Callout>
+
 ## Receipt Anatomy
 
 | Field | Meaning | Notes |