More email SKU shenanigans, now with more TEST labels!

app/models.py

@@ -123,6 +123,11 @@ class Order(Base):
     # isn't the same as it actually being imported, and this app has no
     # way to confirm that manual step happened.
     shipstation_sent_at = Column(DateTime, nullable=True)
+    # Label ID of the "dummy" outbound shipment created for the emailed-
+    # return-label workflow, persisted so it's verifiable (in ShipStation's
+    # own UI) as a separate step before creating the real return label
+    # from it - rather than both happening invisibly in one call.
+    dummy_outbound_label_id = Column(String(64), nullable=True)
 
     # Legacy/unused - kept only because SQLite doesn't make dropping a
     # column free and nothing reads this. Don't confuse with `packed`