fix: hide operators' internal back-move reasons from the customer's order history

A move back undoes an operator's mistake and its reason is internal. The
customer's history now omits back moves and shows a reason only for a
correction; the smoke test checks both.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

tests/smoke_test.py

@@ -195,6 +195,11 @@ def run():
     client.call('/operator/orders/'+oid+'/move',{'state':'fin','version':version},operator=True);version+=1
     history=client.call('/operator/orders/'+oid+'/history',operator=True)
     assert len(history)==8 and history[-2]['back'] and history[-2]['reason']=='Movido por engano' and not history[-1]['back']
+    # The customer sees the stages and the correction's reason, never the
+    # internal reason for going back.
+    seen=client.call('/customer/orders/'+oid)['history']
+    assert len(seen)==7 and all(h['reason']=='' or h['to_state']=='cor' for h in seen)
+    assert any(h['to_state']=='cor' and h['reason']=='Local test correction' for h in seen)
     print('PASS: a mistaken move is undone one stage back with a reason, without messaging the customer again')
     print('PASS: all modes, authoritative review/prices/freight, tamper rejection, concurrent payment idempotency, transitions and history')
     deadline=time.monotonic()+30