feat: send digest and honor existing CID on global stamp

tests/test_global_client.py

@@ -60,7 +60,10 @@ async def test_global_stamp_posts_hash_sync_and_maps_receipt():
     method, url, payload, headers = http.calls[0]
     assert method == "POST"
     assert url == "https://api.veraetime.net/api/timestamp"
-    assert payload == {"data": SHA256_EMPTY, "hashAlg": "SHA256"}
+    assert payload["data"] == SHA256_EMPTY
+    assert payload["digest"] == SHA256_EMPTY
+    assert payload["hashAlg"] == "SHA256"
+    assert payload["restamp"] is False
     assert headers["Authorization"] == "Bearer secret"
     assert rec.scope == "global"
     assert rec.receipt_id == "job-1"