feat: 非精油产品(drop_count=1)显示"份"而非"滴"

oils store新增 unitLabel/unitLabelPlural，根据 dropCount 判断：
- 精油(dropCount>1): 滴/drop
- 护肤品等(dropCount=1): 份/portion
影响: 配方卡片、个人配方、库存匹配、去重提示

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

frontend/src/views/MyDiary.vue

@@ -31,7 +31,7 @@
           <div class="diary-name">{{ d.name || '未命名' }}</div>
           <div class="diary-ings">
             <span v-for="ing in (d.ingredients || []).slice(0, 3)" :key="ing.oil" class="diary-ing">
-              {{ ing.oil }} {{ ing.drops }}滴
+              {{ ing.oil }} {{ ing.drops }}{{ oils.unitLabel(ing.oil) }}
             </span>
             <span v-if="(d.ingredients || []).length > 3" class="diary-more">+{{ (d.ingredients || []).length - 3 }}</span>
           </div>