Translate UI and user-facing messages to Ukrainian (#5)

- All frontend pages, labels, notices and errors; html lang=uk, uk-UA money format
- Brand "Assistant System" in the top bar and page title
- Backend error details returned to the UI (auth, orders, receipts,
  cash registers, Checkbox/CRM/NP errors) and CLI output
- Tests updated for the new messages

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

backend/tests/test_nova_poshta_client.py

@@ -110,7 +110,7 @@ class TestNpTrackingClientGetStatuses:
     async def test_rejects_too_many_documents(self) -> None:
         client = NpTrackingClient()
 
-        with pytest.raises(NovaPoshtaError, match="Слишком много"):
+        with pytest.raises(NovaPoshtaError, match="Забагато"):
             await client.get_statuses(
                 api_key=API_KEY, waybill_numbers=[str(i) for i in range(101)]
             )

backend/tests/test_orders_router.py

@@ -88,7 +88,7 @@ def _patch_orders_service(monkeypatch: pytest.MonkeyPatch) -> None:
         session: object, order_id: str, data: object
     ) -> tuple[Order, list[str]] | None:
         if order_id == "locked":
-            raise orders_router.orders_service.OrderEditError("По заказу уже создан чек")
+            raise orders_router.orders_service.OrderEditError("За замовленням уже створено чек")
         if order_id != "1":
             return None
         order = _order(order_id)

backend/tests/test_orders_service.py

@@ -140,16 +140,16 @@ class TestUpdateOrder:
         assert order.goods == [stored]
 
     def test_total_above_goods_sum_is_rejected(self) -> None:
-        with pytest.raises(OrderEditError, match="больше суммы товаров"):
+        with pytest.raises(OrderEditError, match="більша за суму товарів"):
             _update(_order(), _payload(total_amount="1200.00"))
 
     def test_discount_above_line_sum_is_rejected(self) -> None:
         good = {"name": "Товар", "price": "10.00", "quantity": "1", "discount_amount": "11"}
-        with pytest.raises(OrderEditError, match="скидка больше"):
+        with pytest.raises(OrderEditError, match="знижка більша"):
             _update(_order(), _payload(goods=[good], total_amount="0"))
 
     def test_order_with_receipt_is_locked(self) -> None:
-        with pytest.raises(OrderEditError, match="уже создан чек"):
+        with pytest.raises(OrderEditError, match="уже створено чек"):
             _update(_order(receipt_created_at=datetime.now(UTC)), _payload())
 
     def test_missing_or_deleted_order_returns_none(self) -> None:

backend/tests/test_receipts_router.py

@@ -45,7 +45,9 @@ def queue(monkeypatch: pytest.MonkeyPatch) -> FakeQueue:
     )
 
     async def fake_request(session: Any, items: Any, *, user: Any, request: Any) -> Any:
-        return receipts_service.RequestResult(created=[receipt], errors={"2": "У заказа нет ТТН"})
+        return receipts_service.RequestResult(
+            created=[receipt], errors={"2": "У замовлення немає ТТН"}
+        )
 
     async def fake_commit(self: AsyncSession) -> None:
         return None
@@ -74,5 +76,5 @@ def test_cashier_creates_and_enqueues(queue: FakeQueue) -> None:
     assert response.status_code == 202
     body = response.json()
     assert [r["order_id"] for r in body["created"]] == ["1"]
-    assert body["errors"] == {"2": "У заказа нет ТТН"}
+    assert body["errors"] == {"2": "У замовлення немає ТТН"}
     assert queue.jobs == [("create_ettn_receipt", (body["created"][0]["id"],))]

backend/tests/test_receipts_service.py

@@ -77,17 +77,17 @@ class TestResolveAmounts:
         assert amounts.cod_kopecks == 100000
 
     def test_explicit_prepayment_must_match_cod(self) -> None:
-        with pytest.raises(svc.ReceiptValidationError, match="≠ наложка"):
+        with pytest.raises(svc.ReceiptValidationError, match="≠ післяплата"):
             svc.resolve_amounts(_order(np_cod_amount_kopecks=100000), 10000)
 
     @pytest.mark.parametrize(
         ("overrides", "message"),
         [
-            ({"waybill_number": None}, "нет ТТН"),
-            ({"np_cod_amount_kopecks": None}, "контроля оплаты"),
-            ({"np_status_code": "9"}, "не в пути"),
-            ({"np_cod_amount_kopecks": 130000}, "больше суммы заказа"),
-            ({"is_deleted": True}, "удалён"),
+            ({"waybill_number": None}, "немає ТТН"),
+            ({"np_cod_amount_kopecks": None}, "контролю оплати"),
+            ({"np_status_code": "9"}, "не в дорозі"),
+            ({"np_cod_amount_kopecks": 130000}, "більша за суму замовлення"),
+            ({"is_deleted": True}, "видалено"),
         ],
     )
     def test_rejects(self, overrides: dict[str, Any], message: str) -> None:
@@ -226,7 +226,7 @@ class TestRequestReceipts:
         )
 
         assert result.created == []
-        assert "Касса не определена" in result.errors[order.id]
+        assert "Касу не визначено" in result.errors[order.id]
 
 
 class FakeSession:
@@ -289,7 +289,7 @@ class TestCreateEttn:
         await svc.create_ettn_for_receipt(FakeSession(order, register, receipt), client, receipt.id)
 
         assert receipt.status == ReceiptStatus.FAILED
-        assert "уже привязана" in (receipt.error or "")
+        assert "вже прив'язана" in (receipt.error or "")
         assert order.receipt_created_at is None
 
     async def test_unavailable_keeps_pending_then_reconciles(self) -> None: