feat(client): 二维码打印功能

在商品详情二维码弹窗中新增「打印」按钮，使用 printing + pdf
生成含商品名称、编号、规格和二维码图片的 PDF，触发浏览器打印对话框。
嵌入 NotoSansSC-Regular 字体保证中文正常显示。

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

client/lib/screens/products/product_detail_screen.dart

@@ -4,6 +4,9 @@ import 'package:flutter/foundation.dart';
 import 'package:flutter/material.dart';
 import 'package:flutter/services.dart';
 import 'package:flutter_riverpod/flutter_riverpod.dart';
+import 'package:pdf/pdf.dart';
+import 'package:pdf/widgets.dart' as pw;
+import 'package:printing/printing.dart';
 import '../../core/config/app_config.dart';
 import '../../core/theme/app_theme.dart';
 import '../../models/product.dart';
@@ -152,7 +155,7 @@ class _ProductDetailScreenState extends ConsumerState<ProductDetailScreen> {
   void _showQRCode() {
     showDialog(
       context: context,
-      builder: (_) => _QRCodeDialog(productId: widget.productId),
+      builder: (_) => _QRCodeDialog(productId: widget.productId, product: _product!),
     );
   }
 
@@ -498,7 +501,8 @@ class _UploadButton extends StatelessWidget {
 
 class _QRCodeDialog extends ConsumerStatefulWidget {
   final int productId;
-  const _QRCodeDialog({required this.productId});
+  final Product product;
+  const _QRCodeDialog({required this.productId, required this.product});
 
   @override
   ConsumerState<_QRCodeDialog> createState() => _QRCodeDialogState();
@@ -506,13 +510,51 @@ class _QRCodeDialog extends ConsumerStatefulWidget {
 
 class _QRCodeDialogState extends ConsumerState<_QRCodeDialog> {
   late Future<Uint8List> _future;
+  Uint8List? _bytes;
+  bool _printing = false;
 
   @override
   void initState() {
     super.initState();
     _future = ref
         .read(productRepositoryProvider)
-        .getQRCodeBytes(widget.productId);
+        .getQRCodeBytes(widget.productId)
+      ..then((b) => _bytes = b);
+  }
+
+  Future<void> _print() async {
+    if (_bytes == null || _printing) return;
+    setState(() => _printing = true);
+    try {
+      final fontData = await rootBundle.load('assets/fonts/NotoSansSC-Regular.ttf');
+      final font = pw.Font.ttf(fontData);
+      final p = widget.product;
+      final doc = pw.Document();
+      final qrImage = pw.MemoryImage(_bytes!);
+      doc.addPage(pw.Page(
+        pageFormat: PdfPageFormat.a4,
+        build: (_) => pw.Center(
+          child: pw.Column(
+            mainAxisSize: pw.MainAxisSize.min,
+            children: [
+              pw.Image(qrImage, width: 200, height: 200),
+              pw.SizedBox(height: 12),
+              pw.Text(p.name,
+                  style: pw.TextStyle(font: font, fontSize: 18, fontWeight: pw.FontWeight.bold)),
+              pw.SizedBox(height: 4),
+              pw.Text('编号：${p.code}',
+                  style: pw.TextStyle(font: font, fontSize: 13)),
+              if ((p.spec ?? '').isNotEmpty)
+                pw.Text('规格：${p.spec}',
+                    style: pw.TextStyle(font: font, fontSize: 13)),
+            ],
+          ),
+        ),
+      ));
+      await Printing.layoutPdf(onLayout: (_) async => doc.save());
+    } finally {
+      if (mounted) setState(() => _printing = false);
+    }
   }
 
   @override
@@ -520,8 +562,8 @@ class _QRCodeDialogState extends ConsumerState<_QRCodeDialog> {
     return AlertDialog(
       title: const Text('商品二维码'),
       content: SizedBox(
-        width: 200,
-        height: 200,
+        width: 220,
+        height: 220,
         child: FutureBuilder<Uint8List>(
           future: _future,
           builder: (_, snap) {
@@ -540,6 +582,15 @@ class _QRCodeDialogState extends ConsumerState<_QRCodeDialog> {
           onPressed: () => Navigator.of(context).pop(),
           child: const Text('关闭'),
         ),
+        FilledButton.icon(
+          onPressed: _bytes == null ? null : (_printing ? null : _print),
+          icon: _printing
+              ? const SizedBox(
+                  width: 14, height: 14,
+                  child: CircularProgressIndicator(strokeWidth: 2, color: Colors.white))
+              : const Icon(Icons.print, size: 16),
+          label: const Text('打印'),
+        ),
       ],
     );
   }

client/pubspec.lock

@@ -25,6 +25,22 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.13.1"
+  barcode:
+    dependency: transitive
+    description:
+      name: barcode
+      sha256: "7b6729c37e3b7f34233e2318d866e8c48ddb46c1f7ad01ff7bb2a8de1da2b9f4"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.2.9"
+  bidi:
+    dependency: transitive
+    description:
+      name: bidi
+      sha256: "77f475165e94b261745cf1032c751e2032b8ed92ccb2bf5716036db79320637d"
+      url: "https://pub.dev"
+    source: hosted
+    version: "2.0.13"
   boolean_selector:
     dependency: transitive
     description:
@@ -232,6 +248,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "4.1.2"
+  image:
+    dependency: transitive
+    description:
+      name: image
+      sha256: f31d52537dc417fdcde36088fdf11d191026fd5e4fae742491ebd40e5a8bea7d
+      url: "https://pub.dev"
+    source: hosted
+    version: "4.3.0"
   intl:
     dependency: "direct main"
     description:
@@ -392,6 +416,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "1.9.1"
+  path_parsing:
+    dependency: transitive
+    description:
+      name: path_parsing
+      sha256: "883402936929eac138ee0a45da5b0f2c80f89913e6dc3bf77eb65b84b409c6ca"
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.1.0"
   path_provider:
     dependency: "direct main"
     description:
@@ -440,6 +472,22 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.3.0"
+  pdf:
+    dependency: "direct main"
+    description:
+      name: pdf
+      sha256: e47a275b267873d5944ad5f5ff0dcc7ac2e36c02b3046a0ffac9b72fd362c44b
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.12.0"
+  pdf_widget_wrapper:
+    dependency: transitive
+    description:
+      name: pdf_widget_wrapper
+      sha256: c930860d987213a3d58c7ec3b7ecf8085c3897f773e8dc23da9cae60a5d6d0f5
+      url: "https://pub.dev"
+    source: hosted
+    version: "1.0.4"
   petitparser:
     dependency: transitive
     description:
@@ -464,6 +512,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.1.8"
+  printing:
+    dependency: "direct main"
+    description:
+      name: printing
+      sha256: "689170c9ddb1bda85826466ba80378aa8993486d3c959a71cd7d2d80cb606692"
+      url: "https://pub.dev"
+    source: hosted
+    version: "5.14.3"
   pub_semver:
     dependency: transitive
     description:
@@ -472,6 +528,14 @@ packages:
       url: "https://pub.dev"
     source: hosted
     version: "2.2.0"
+  qr:
+    dependency: transitive
+    description:
+      name: qr
+      sha256: "5a1d2586170e172b8a8c8470bbbffd5eb0cd38a66c0d77155ea138d3af3a4445"
+      url: "https://pub.dev"
+    source: hosted
+    version: "3.0.2"
   record_use:
     dependency: transitive
     description:

client/pubspec.yaml

@@ -20,6 +20,8 @@ dependencies:
   excel: ^4.0.6
   path_provider: ^2.1.0
   file_picker: ^8.1.6
+  printing: ^5.13.0
+  pdf: ^3.10.8
 
 dev_dependencies:
   flutter_test:
@@ -29,3 +31,6 @@ dev_dependencies:
 
 flutter:
   uses-material-design: true
+
+  assets:
+    - assets/fonts/NotoSansSC-Regular.ttf