fix: 预览品牌名保留换行，配方卡片与预览布局一致

- 预览QR文字加 white-space: pre-line 保留换行
- 配方卡片结构: QR+品牌名(absolute右上) → 内容区(padding-right避让)
  → 精油列表(每行9px间距) → 总成本(绿色条) → Logo左+日期右
- 两者布局完全一致

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/views/MyDiary.vue

@@ -1091,8 +1091,9 @@ async function applyBusiness() {
   font-size: 6px;
   color: var(--text-light);
   line-height: 1.2;
-  word-break: break-all;
+  white-space: pre-line;
   max-width: 50px;
+  text-align: center;
 }
 .card-preview-cost {
   position: relative;