Set CRM order status to PACKED after Checkbox accepts the receipt

- ExoCrmClient.set_status: live SetStatus needs {Orders: [id], Status} and
  replies per order, unlike the documented {ID, Status}
- receipts.crm_status_set_at (migration 0006); set right after creation,
  retried by cron, row-locked to avoid a repeat PACKED overwriting a newer status
- CRM errors under capitalized 'Errors' and non-JSON replies are reported

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

backend/tests/test_crm_client.py

@@ -106,3 +106,43 @@ class TestExoCrmClientGetOrders:
 
         with pytest.raises(CrmError, match="Checksum Error"):
             await client.get_orders(status="APPROVED")
+
+
+class TestExoCrmClientSetStatus:
+    @respx.mock
+    async def test_sends_order_list_and_parses_per_order_result(self) -> None:
+        import json
+
+        route = respx.post(BASE_URL).mock(
+            return_value=Response(
+                200,
+                json={
+                    "<": "<",
+                    "123901": {"Status": "Success", "ChangeStatus": "Success"},
+                    ">": ">",
+                },
+            )
+        )
+
+        await ExoCrmClient(_settings()).set_status(order_id="123901", status="PACKED")
+
+        body = json.loads(route.calls.last.request.content)
+        assert body["object"] == "Orders"
+        assert body["method"] == "SetStatus"
+        # Не {"ID": ...} из документации — боевая CRM принимает только список в Orders.
+        assert body["params"] == {"Orders": ["123901"], "Status": "PACKED"}
+        assert "md5sum" in body
+
+    @respx.mock
+    async def test_raises_on_capitalized_errors(self) -> None:
+        respx.post(BASE_URL).mock(
+            return_value=Response(200, json={"<": "<", "Errors": ["Undefined order list."]})
+        )
+        with pytest.raises(CrmError, match="Undefined order list"):
+            await ExoCrmClient(_settings()).set_status(order_id="1", status="PACKED")
+
+    @respx.mock
+    async def test_raises_on_non_json_reply(self) -> None:
+        respx.post(BASE_URL).mock(return_value=Response(200, text="<b>Notice</b>: ..."))
+        with pytest.raises(CrmError, match="не JSON"):
+            await ExoCrmClient(_settings()).set_status(order_id="1", status="PACKED")