fix(client): 打印异常加 try-catch，错误以 SnackBar 提示用户

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

client/lib/core/utils/print_util_stub.dart

@@ -189,7 +189,11 @@ Future<void> printProductLabelImpl({
     ),
   ));
 
-  await Printing.layoutPdf(onLayout: (_) async => doc.save());
+  try {
+    await Printing.layoutPdf(onLayout: (_) async => doc.save());
+  } catch (e) {
+    throw Exception('打印失败，请检查打印机连接和驱动是否正常。\n详情：$e');
+  }
 }
 
 pw.Widget _label2ColRow(
@@ -424,7 +428,11 @@ Future<void> printStockInOrderImpl(StockInOrder order) async {
       ),
     ],
   ));
-  await Printing.layoutPdf(onLayout: (_) async => doc.save());
+  try {
+    await Printing.layoutPdf(onLayout: (_) async => doc.save());
+  } catch (e) {
+    throw Exception('打印失败，请检查打印机连接和驱动是否正常。\n详情：$e');
+  }
 }
 
 Future<void> printStockOutOrderImpl(StockOutOrder order) async {
@@ -474,5 +482,9 @@ Future<void> printStockOutOrderImpl(StockOutOrder order) async {
       ),
     ],
   ));
-  await Printing.layoutPdf(onLayout: (_) async => doc.save());
+  try {
+    await Printing.layoutPdf(onLayout: (_) async => doc.save());
+  } catch (e) {
+    throw Exception('打印失败，请检查打印机连接和驱动是否正常。\n详情：$e');
+  }
 }

client/lib/screens/stock_in/stock_in_list_screen.dart

@@ -247,8 +247,16 @@ class _StockInListScreenState extends ConsumerState<StockInListScreen> {
               ),
               TextButton(
                 onPressed: () async {
-                  final order = await ref.read(stockInRepositoryProvider).get(o.id);
-                  await printStockInOrder(order);
+                  try {
+                    final order = await ref.read(stockInRepositoryProvider).get(o.id);
+                    await printStockInOrder(order);
+                  } catch (e) {
+                    if (context.mounted) {
+                      ScaffoldMessenger.of(context).showSnackBar(
+                        SnackBar(content: Text(e.toString()), backgroundColor: Colors.red),
+                      );
+                    }
+                  }
                 },
                 child: const Text('打印',
                     style: TextStyle(fontSize: 12, color: AppTheme.primary)),
@@ -690,7 +698,17 @@ class _StockInDetailDialogState extends ConsumerState<_StockInDetailDialog> {
                     IconButton(
                       icon: const Icon(Icons.print_outlined, color: Colors.white),
                       tooltip: '打印',
-                      onPressed: () => printStockInOrder(_loadedOrder!),
+                      onPressed: () async {
+                        try {
+                          await printStockInOrder(_loadedOrder!);
+                        } catch (e) {
+                          if (context.mounted) {
+                            ScaffoldMessenger.of(context).showSnackBar(
+                              SnackBar(content: Text(e.toString()), backgroundColor: Colors.red),
+                            );
+                          }
+                        }
+                      },
                     ),
                   IconButton(
                     icon: const Icon(Icons.close, color: Colors.white),

client/lib/screens/stock_out/stock_out_list_screen.dart

@@ -254,8 +254,16 @@ class _StockOutListScreenState extends ConsumerState<StockOutListScreen> {
               ),
               TextButton(
                 onPressed: () async {
-                  final order = await ref.read(stockOutRepositoryProvider).get(o.id);
-                  await printStockOutOrder(order);
+                  try {
+                    final order = await ref.read(stockOutRepositoryProvider).get(o.id);
+                    await printStockOutOrder(order);
+                  } catch (e) {
+                    if (context.mounted) {
+                      ScaffoldMessenger.of(context).showSnackBar(
+                        SnackBar(content: Text(e.toString()), backgroundColor: Colors.red),
+                      );
+                    }
+                  }
                 },
                 child: const Text('打印',
                     style: TextStyle(fontSize: 12, color: AppTheme.primary)),
@@ -682,7 +690,17 @@ class _StockOutDetailDialogState extends ConsumerState<_StockOutDetailDialog> {
                     IconButton(
                       icon: const Icon(Icons.print_outlined, color: Colors.white),
                       tooltip: '打印',
-                      onPressed: () => printStockOutOrder(_loadedOrder!),
+                      onPressed: () async {
+                        try {
+                          await printStockOutOrder(_loadedOrder!);
+                        } catch (e) {
+                          if (context.mounted) {
+                            ScaffoldMessenger.of(context).showSnackBar(
+                              SnackBar(content: Text(e.toString()), backgroundColor: Colors.red),
+                            );
+                          }
+                        }
+                      },
                     ),
                   IconButton(
                     icon: const Icon(Icons.close, color: Colors.white),