feat: 打印预览组件化

miniprogram/englishPages/letterTracing/letterTracing.wxml

@@ -2,18 +2,13 @@
 
 <view class="lt-page">
     <view class="lt-main">
-        <view class="lt-preview-wrap">
-            <view class="lt-preview-card">
-                <text class="lt-preview-kicker">打印预览</text>
-                <view id="canvasWrapper" class="lt-canvas-wrap">
-                    <canvas
-                        type="2d"
-                        id="canvasContent"
-                        class="lt-canvas"
-                        style="width:{{boxWidth}}px;height:{{boxHeight}}px" />
-                </view>
-            </view>
-        </view>
+        <preview-card
+            id="previewCard"
+            showRefresh="{{false}}"
+            showFavorite="{{true}}"
+            favorited="{{isPreviewFavorite}}"
+            bind:canvas-ready="onCanvasReady"
+            bind:favorite="onPreviewFavorite" />
 
         <!-- 练习类型（2列卡片网格） -->
         <view class="lt-section">