fix(frontend): 流转蓝图 + 聊天室 + 卡片布局 + 打印功能修复

1. TreeCanvas.vue - Y轴坐标算法重构:
   - calcSubtreeHeight 改为兄弟累加 (reduce) 替代 Math.max，彻底杜绝垂直重叠
   - childNode.y = parentNode.y + CARD_H + VERTICAL_GAP 严格向下延伸
   - 同级子节点按子树高度累加 startY，各占独立 Y 区域
   - 加宽画布默认尺寸 (400→800, padding +300/+400)

2. detail.vue - onShow 生命周期修复:
   - 新增 onShow() 钩子调用 fetchMessages()，解决聊天室退回不刷新问题

3. TaskSwipeCards.vue + detail.vue - CSS 防跳动:
   - .ss-swiper-h / .ss-card-wrapper 添加 min-height: 220px
   - .card 添加 min-height: 120px

4. detail.vue - 移动端打印标签:
   - 新增「🖨️ 打印标签」按钮
   - 双方案 ActionSheet: 网络打印机(后端API) / 蓝牙打印机(ESC/POS)
   - 对接现有 /print/execute 端点

track-uniapp/src/pages/scan/components/TaskSwipeCards.vue

@@ -212,9 +212,9 @@ export default {
 .ss-overview-btn { font-size: 12px; font-weight: 700; color: #2563eb; padding: 5px 10px; background: #dbeafe; border-radius: 8px; }
 
 /* 滑动区域 */
-.ss-swiper-h { width: 100%; flex: 1; }
+.ss-swiper-h { width: 100%; flex: 1; min-height: 220px; }
 .ss-swiper-v { width: 100%; }
-.ss-card-wrapper { display: flex; align-items: flex-start; justify-content: center; padding: 10px 16px; height: 100%; box-sizing: border-box; }
+.ss-card-wrapper { display: flex; align-items: flex-start; justify-content: center; padding: 10px 16px; height: 100%; min-height: 220px; box-sizing: border-box; }
 
 /* 任务卡片 */
 .ss-card { position: relative; width: 100%; max-width: 420px; background: #fff; border-radius: 20px; padding: 18px 22px; box-shadow: 0 8px 24px rgba(0,0,0,0.1); display: flex; flex-direction: column; gap: 10px; max-height: 100%; overflow-y: auto; }