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/core/utils/print_util_stub.dart

@@ -501,7 +501,7 @@ Future<List<String>> listLabelPrintersImpl() async {
         return (r.stdout as String)
             .split('\n')
             .map((s) => s.trim())
-            .where((s) => s.isNotEmpty)
+            .where((s) => s.isNotEmpty && _isThermalName(s))
             .toList();
       }
     } catch (e) {
@@ -511,7 +511,10 @@ Future<List<String>> listLabelPrintersImpl() async {
   }
   if (Platform.isWindows) {
     try {
-      return (await Printing.listPrinters()).map((p) => p.name).toList();
+      return (await Printing.listPrinters())
+          .map((p) => p.name)
+          .where((n) => _isThermalName(n))
+          .toList();
     } catch (e) {
       debugPrint('[label] listPrinters 失败: $e');
     }

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)),
                                         )

client/lib/widgets/label_preview_dialog.dart

@@ -36,6 +36,7 @@ class _LabelPreviewDialogState extends State<LabelPreviewDialog> {
   List<String> _printers = [];
   String? _printer;
   bool _printing = false;
+  bool _printersChecked = false;
   String _status = '';
 
   @override
@@ -63,6 +64,7 @@ class _LabelPreviewDialogState extends State<LabelPreviewDialog> {
       setState(() {
         _printers = printers;
         _printer = selected;
+        _printersChecked = true;
       });
     }
 
@@ -147,6 +149,7 @@ class _LabelPreviewDialogState extends State<LabelPreviewDialog> {
         _printing = false;
         _status = '完成，共打印 $done 张';
       });
+      Navigator.of(context).pop();
     }
   }
 
@@ -329,8 +332,9 @@ class _LabelPreviewDialogState extends State<LabelPreviewDialog> {
                   const SizedBox(width: 8),
                   Expanded(
                     child: _printers.isEmpty
-                        ? const Text('检测中或未检测到打印机...',
-                            style: TextStyle(
+                        ? Text(
+                            _printersChecked ? '无打印机可用' : '正在检测打印机...',
+                            style: const TextStyle(
                                 fontSize: 13,
                                 color: AppTheme.textSecondary))
                         : DropdownButtonHideUnderline(
@@ -419,7 +423,9 @@ class _LabelPreviewDialogState extends State<LabelPreviewDialog> {
                   ),
                   const SizedBox(width: 8),
                   FilledButton(
-                    onPressed: (_printing || totalCount == 0) ? null : _doPrint,
+                    onPressed: (_printing || totalCount == 0 || _printer == null)
+                        ? null
+                        : _doPrint,
                     child: Text(
                         _printing ? '打印中...' : '打印 $totalCount 张'),
                   ),