fix: 配方卡片零售价列对齐，缺零售价的行留空占位

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

frontend/src/components/RecipeDetailOverlay.vue

@@ -66,7 +66,7 @@
                 <span class="ec-oil-name">{{ getCardOilName(ing.oil) }}</span>
                 <span class="ec-drops">{{ ing.drops }} {{ oilsStore.unitLabelPlural(ing.oil, ing.drops, cardLang) }}</span>
                 <span class="ec-cost">{{ oilsStore.fmtPrice(oilsStore.pricePerDrop(ing.oil) * ing.drops) }}</span>
-                <span v-if="hasRetailForOil(ing.oil) && retailPerDrop(ing.oil) > oilsStore.pricePerDrop(ing.oil)" class="ec-retail">{{ oilsStore.fmtPrice(retailPerDrop(ing.oil) * ing.drops) }}</span>
+                <span v-if="cardHasAnyRetail" class="ec-retail">{{ hasRetailForOil(ing.oil) && retailPerDrop(ing.oil) > oilsStore.pricePerDrop(ing.oil) ? oilsStore.fmtPrice(retailPerDrop(ing.oil) * ing.drops) : '' }}</span>
               </li>
             </ul>
 
@@ -590,6 +590,10 @@ function getCardRecipeName() {
   return displayRecipe.value.name
 }
 
+const cardHasAnyRetail = computed(() =>
+  cardIngredients.value.some(ing => hasRetailForOil(ing.oil) && retailPerDrop(ing.oil) > oilsStore.pricePerDrop(ing.oil))
+)
+
 const cardTitleSize = computed(() => {
   const name = getCardRecipeName()
   const len = name.length