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/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: