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/products/product_detail_screen.dart

@@ -528,10 +528,10 @@ class _QRCodeDialogState extends ConsumerState<_QRCodeDialog> {
   Future<void> _print() async {
     if (_bytes == null || _printing) return;
     setState(() { _printing = true; _printStatus = '正在打印...'; });
+    final p = widget.product;
+    final shopInfo = ref.read(shopInfoProvider).valueOrNull;
     try {
-      final p = widget.product;
-      final shopInfo = ref.read(shopInfoProvider).valueOrNull;
-      await printProductLabel(
+      await safePrint(context, () => printProductLabel(
         qrBytes: _bytes!,
         name: p.name,
         code: p.code,
@@ -540,13 +540,7 @@ class _QRCodeDialogState extends ConsumerState<_QRCodeDialog> {
         shopName: shopInfo?.name ?? '',
         shopAddress: shopInfo?.address ?? '',
         shopPhone: shopInfo?.phone ?? '',
-      );
-    } catch (e) {
-      if (mounted) {
-        ScaffoldMessenger.of(context).showSnackBar(
-          SnackBar(content: Text('打印失败：$e'), backgroundColor: Colors.red),
-        );
-      }
+      ));
     } finally {
       if (mounted) setState(() { _printing = false; _printStatus = ''; });
     }