fix(client): 修复标签打印预览三个问题

- 打印完成后自动关闭预览弹窗
- 打印机列表改为仅显示热敏打印机，无热敏打印机时显示"无打印机可用"并禁用打印按钮
- 库存列表表格行"打标签"按钮改为调用预览弹窗（之前仍走旧直接打印逻辑）

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

client/lib/screens/inventory/inventory_list_screen.dart

@@ -668,27 +668,7 @@ class _InventoryListScreenState extends ConsumerState<InventoryListScreen> {
                                 DataCell(
                                   item.productId != null
                                       ? TextButton(
-                                          onPressed: () async {
-                                            final qrBytes = await ref
-                                                .read(productRepositoryProvider)
-                                                .getQRCodeBytes(item.productId!);
-                                            final shopInfo = ref.read(shopInfoProvider).valueOrNull;
-                                            if (context.mounted) {
-                                              await safePrint(context, () => printProductLabel(
-                                                qrBytes: qrBytes,
-                                                name: item.productName,
-                                                code: item.productCode,
-                                                series: item.series.isEmpty ? null : item.series,
-                                                spec: item.spec.isEmpty ? null : item.spec,
-                                                batchNo: item.batchNo.isEmpty ? null : item.batchNo,
-                                                productionDate: item.productionDate,
-                                                remark: item.remark.isEmpty ? null : item.remark,
-                                                shopName: shopInfo?.name ?? '',
-                                                shopAddress: shopInfo?.address ?? '',
-                                                shopPhone: shopInfo?.phone ?? '',
-                                              ));
-                                            }
-                                          },
+                                          onPressed: () => _printLabel(context, item),
                                           child: const Text('打标签',
                                               style: TextStyle(fontSize: 12, color: AppTheme.primary)),
                                         )