fix(client): 统一打印错误处理，失败时上报并弹提示

新增 safePrint 封装，所有打印调用点统一 catch 任意异常（含字体加载失败），
自动上报 error_reporter 并展示 SnackBar，不再静默失败。

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

client/lib/screens/inventory/inventory_list_screen.dart

@@ -485,12 +485,12 @@ class _InventoryListScreenState extends ConsumerState<InventoryListScreen> {
                                   item.productId != null
                                       ? TextButton(
                                           onPressed: () async {
-                                            try {
-                                              final qrBytes = await ref
-                                                  .read(productRepositoryProvider)
-                                                  .getQRCodeBytes(item.productId!);
-                                              final shopInfo = ref.read(shopInfoProvider).valueOrNull;
-                                              await printProductLabel(
+                                            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,
@@ -502,14 +502,7 @@ class _InventoryListScreenState extends ConsumerState<InventoryListScreen> {
                                                 shopName: shopInfo?.name ?? '',
                                                 shopAddress: shopInfo?.address ?? '',
                                                 shopPhone: shopInfo?.phone ?? '',
-                                              );
-                                            } catch (e) {
-                                              if (context.mounted) {
-                                                ScaffoldMessenger.of(context).showSnackBar(
-                                                  SnackBar(content: Text('打印失败：$e'),
-                                                      backgroundColor: AppTheme.danger),
-                                                );
-                                              }
+                                              ));
                                             }
                                           },
                                           child: const Text('打标签',