feat: dukung penjualan produk per timbangan

Produk kini punya cara jual `unit` (cacah) atau `weight` (timbangan),
mengikuti kontrak backend di docs/integration-weight-based-products.md.

- tipe SellBy, domain/infrastructure unit baru, dan endpoint /api/v1/units
- dialog input berat saat produk timbangan ditambahkan ke keranjang
- tiap penimbangan jadi baris keranjang sendiri; total baris dihitung
  berat x harga satuan, sedangkan produk cacah tetap digabung
- request ke backend mengirim quantity 1 dan membawa berat
- migrasi DB v3: kolom sell_by, unit_id, unit_name, unit_abbreviation
  di tabel products supaya satuan tetap tampil saat offline
- tampilan keranjang, struk, split bill, void, dan refund memakai berat
- test/weight_based_products_test.dart menutup perilaku di atas (9 test)

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

lib/presentation/pages/order/pages/success_add_item_order/widgets/success_add_item_order_right_panel.dart

@@ -3,6 +3,7 @@ import 'package:flutter/material.dart';
 import '../../../../../../application/checkout/checkout_form/checkout_form_bloc.dart';
 import '../../../../../../common/extension/extension.dart';
 import '../../../../../../common/theme/theme.dart';
+import '../../../../../../domain/product/product.dart';
 import '../../../../../components/spaces/space.dart';
 
 class SuccessAddItemOrderRightPanel extends StatelessWidget {
@@ -86,14 +87,7 @@ class SuccessAddItemOrderRightPanel extends StatelessWidget {
                 ],
               ),
               Text(
-                (checkoutState.items.fold(
-                  0,
-                  (previousValue, element) =>
-                      previousValue +
-                      (element.product.price.toInt() +
-                              (element.variant?.priceModifier.toInt() ?? 0)) *
-                          element.quantity,
-                )).toString().currencyFormatRpV2,
+                checkoutState.items.cartTotal.toInt().toString().currencyFormatRpV2,
                 style: AppStyle.md.copyWith(fontWeight: FontWeight.w600),
               ),
             ],
@@ -165,15 +159,10 @@ class SuccessAddItemOrderRightPanel extends StatelessWidget {
                     ],
                   ),
                   child: Text(
-                    (checkoutState.items.fold(
-                      0,
-                      (previousValue, element) =>
-                          previousValue +
-                          (element.product.price.toInt() +
-                                  (element.variant?.priceModifier.toInt() ??
-                                      0)) *
-                              element.quantity,
-                    )).toString().currencyFormatRpV2,
+                    checkoutState.items.cartTotal
+                        .toInt()
+                        .toString()
+                        .currencyFormatRpV2,
                     style: AppStyle.xl.copyWith(
                       fontWeight: FontWeight.bold,
                       color: Colors.white,
@@ -270,7 +259,7 @@ class SuccessAddItemOrderRightPanel extends StatelessWidget {
                   borderRadius: BorderRadius.circular(12),
                 ),
                 child: Text(
-                  '${item.quantity}x',
+                  (item.isWeighted ? item.quantityLabel : "${item.quantity}x"),
                   style: AppStyle.md.copyWith(
                     fontWeight: FontWeight.bold,
                     color: Colors.white,
@@ -279,11 +268,7 @@ class SuccessAddItemOrderRightPanel extends StatelessWidget {
               ),
               const SpaceHeight(8),
               Text(
-                ((item.product.price.toInt() +
-                            (item.variant?.priceModifier.toInt() ?? 0)) *
-                        item.quantity)
-                    .toString()
-                    .currencyFormatRpV2,
+                item.lineTotal.toInt().toString().currencyFormatRpV2,
                 style: AppStyle.lg.copyWith(
                   fontWeight: FontWeight.bold,
                   color: AppColor.primary,

lib/presentation/pages/order/pages/success_order/widgets/success_order_right_panel.dart

@@ -255,7 +255,7 @@ class SuccessOrderRightPanel extends StatelessWidget {
                   borderRadius: BorderRadius.circular(12),
                 ),
                 child: Text(
-                  '${item.quantity}x',
+                  (item.isWeighted ? item.quantityLabel : "${item.quantity}x"),
                   style: AppStyle.md.copyWith(
                     fontWeight: FontWeight.bold,
                     color: Colors.white,

lib/presentation/pages/order/widgets/order_list.dart

@@ -211,7 +211,9 @@ class OrderList extends StatelessWidget {
                               borderRadius: BorderRadius.circular(8),
                             ),
                             child: Text(
-                              'x${product.quantity}',
+                              (product.isWeighted
+                                  ? product.quantityLabel
+                                  : "x${product.quantity}"),
                               style: AppStyle.md.copyWith(
                                 fontWeight: FontWeight.w600,
                                 color: AppColor.primary,