fix: QR改为float right自然对齐文字，不再absolute定位

配方卡片:
- QR从.export-card的absolute定位改为.card-content内float right
- QR自然跟"来自大地的礼物"文字顶端对齐
- 右侧边缘跟内容区域对齐（不再需要手动算padding偏移）

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

frontend/src/components/RecipeDetailOverlay.vue

@@ -55,15 +55,12 @@
             class="card-brand-bg"
             :style="{ backgroundImage: `url('${brand.brand_bg}')` }"
           />
-          <div v-if="brand.qr_code" class="card-qr-wrapper">
-            <img
-              :src="brand.qr_code"
-              class="card-qr"
-              crossorigin="anonymous"
-            />
-            <div v-if="brand.brand_name" class="card-qr-name">{{ brand.brand_name }}</div>
-          </div>
           <div class="card-content">
+            <!-- QR floated right, aligns with brand text top -->
+            <div v-if="brand.qr_code" class="card-qr-float">
+              <img :src="brand.qr_code" class="card-qr" crossorigin="anonymous" />
+              <div v-if="brand.brand_name" class="card-qr-name">{{ brand.brand_name }}</div>
+            </div>
             <div class="card-brand-text">
               {{ cardLang === 'en' ? 'doTERRA · Gifts of the Earth' : 'doTERRA · 来自大地的礼物' }}
             </div>
@@ -1141,15 +1138,14 @@ async function saveRecipe() {
   pointer-events: none;
 }
 
-.card-qr-wrapper {
-  position: absolute;
-  top: 36px;
-  right: 36px;
+.card-qr-float {
+  float: right;
   display: flex;
   flex-direction: column;
   align-items: center;
   gap: 3px;
-  z-index: 2;
+  margin-left: 12px;
+  margin-bottom: 8px;
 }
 
 .card-qr {