test: use store timestamps for cleanup compatibility

backend/tests/test_product_archive.py

@@ -1,9 +1,8 @@
-import json
 import hashlib
+import json
 import sqlite3
 import sys
 import shutil
-from datetime import datetime
 from io import BytesIO
 from pathlib import Path
 from types import SimpleNamespace
@@ -336,7 +335,7 @@ def test_archive_version_rejects_failed_cleanup_product_and_status_is_visible(
         f"/api/products/{product['product_id']}", headers=orders_auth_header()
     ).json()
     store = product_archive_client.product_store
-    purge_after = datetime.fromisoformat(deleted["purge_after"])
+    purge_after = store.get_product(deleted["product_id"]).purge_after
     store.claim_product_purge(deleted["product_id"], purge_after)
     store.fail_product_purge(deleted["product_id"])
 
@@ -362,7 +361,7 @@ def test_delete_rejects_failed_cleanup_product_until_restore(product_archive_cli
         f"/api/products/{product['product_id']}", headers=orders_auth_header()
     ).json()
     store = product_archive_client.product_store
-    purge_after = datetime.fromisoformat(deleted["purge_after"])
+    purge_after = store.get_product(deleted["product_id"]).purge_after
     store.claim_product_purge(deleted["product_id"], purge_after)
     store.fail_product_purge(deleted["product_id"], now=purge_after)