fix: 精油详情去掉每ml价格行，只保留每滴价格

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

frontend/src/views/OilReference.vue

@@ -242,10 +242,6 @@
             <span class="detail-label">零售价</span>
             <span class="detail-value">¥ {{ getMeta(selectedOilName).retailPrice.toFixed(2) }}</span>
           </div>
-          <div v-if="!oils.isMlUnit(selectedOilName)" class="detail-row">
-            <span class="detail-label">每ml价格</span>
-            <span class="detail-value">{{ oils.pricePerDrop(selectedOilName) ? ('¥ ' + (oils.pricePerDrop(selectedOilName) * DROPS_PER_ML).toFixed(2)) : '--' }}</span>
-          </div>
 
           <h4 style="margin:16px 0 8px">含此精油的配方</h4>
           <div v-if="recipesWithOil.length" class="detail-recipes">