feat(邀请函): 添加二维码生成功能

- 新增二维码按钮及弹窗界面
- 实现二维码生成、预览和添加到画布功能
- 支持二维码在画布上的拖拽操作
- 添加相关样式和事件处理

index.html

@@ -5,6 +5,7 @@
     <meta name="viewport" content="width=device-width, initial-scale=1.0, maximum-scale=1.0, user-scalable=no">
     <title>极简邀请函制作</title>
     <link rel="stylesheet" href="./css/style.css">
+    <link rel="stylesheet" href="./css/qr.css">
 </head>
 <body>
     <div class="app">
@@ -136,6 +137,27 @@
     <input type="file" id="fileInput" accept="image/*" hidden>
     <canvas id="exportCanvas" hidden></canvas>
 
+    <!-- 二维码功能 -->
+    <button id="qr-btn" title="添加二维码">二维码</button>
+    <div id="qr-modal">
+        <div class="qr-box">
+            <div class="qr-header">
+                <h3>生成二维码</h3>
+                <button class="qr-close">&times;</button>
+            </div>
+            <div class="qr-body">
+                <input type="text" id="qr-input" placeholder="输入网址或文字" maxlength="200">
+                <div id="qr-preview"></div>
+            </div>
+            <div class="qr-footer">
+                <button class="qr-btn qr-cancel">取消</button>
+                <button class="qr-btn qr-ok">添加到画布</button>
+            </div>
+        </div>
+    </div>
+
+    <script src="https://cdnjs.cloudflare.com/ajax/libs/qrcodejs/1.0.0/qrcode.min.js"></script>
     <script src="./js/script.js"></script>
+    <script src="./js/qr.js"></script>
 </body>
 </html>