fix: 配方保存时持久化volume字段，套装对比页复用容量显示逻辑

saveRecipe payload 漏传 selectedVolume 导致编辑器选择的容量从未写入数据库；
套装方案对比页改用与 RecipeCard 一致的 volumeLabel 计算逻辑。

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

frontend/src/components/RecipeDetailOverlay.vue

@@ -1010,6 +1010,7 @@ async function saveRecipe() {
       note: editNote.value.trim(),
       tags: editTags.value,
       ingredients: allIngs,
+      volume: selectedVolume.value || '',
     }
     await recipesStore.saveRecipe(payload)
     // Reload recipes so the data is fresh when re-opened

frontend/src/views/KitExport.vue

@@ -48,7 +48,7 @@
         </thead>
         <tbody>
           <tr v-for="r in activeKitData.recipes" :key="r._id">
-            <td class="td-name">{{ r.name }} <span class="td-volume">{{ r.volume || '单次' }}</span></td>
+            <td class="td-name">{{ r.name }} <span v-if="volumeLabel(r)" class="td-volume">{{ volumeLabel(r) }}</span></td>
             <td class="td-times">{{ calcMaxTimes(r) }}</td>
             <td class="td-cost">{{ fmtPrice(r.kitCost) }}</td>
             <td class="td-cost original">{{ fmtPrice(r.originalCost) }}</td>
@@ -85,7 +85,7 @@
           </thead>
           <tbody>
             <tr v-for="row in crossComparison" :key="row.id">
-              <td class="td-name">{{ row.name }} <span class="td-volume">{{ row.volume || '单次' }}</span></td>
+              <td class="td-name">{{ row.name }} <span v-if="volumeLabel(row)" class="td-volume">{{ volumeLabel(row) }}</span></td>
               <td v-for="ka in kitAnalysis" :key="ka.id" :class="row.costs[ka.id] != null ? 'td-kit-available' : 'td-kit-na'">
                 <template v-if="row.costs[ka.id] != null">{{ fmtPrice(row.costs[ka.id]) }}</template>
                 <template v-else><span class="na">—</span></template>
@@ -120,6 +120,33 @@ const sellingPrices = ref({})
 
 const activeKitData = computed(() => kitAnalysis.value.find(k => k.id === activeKit.value))
 
+function volumeLabel(recipe) {
+  const vol = recipe.volume
+  if (vol) {
+    if (vol === 'single') return '单次'
+    if (vol === 'custom') return ''
+    if (/^\d+$/.test(vol)) return `${vol}ml`
+    return vol
+  }
+  const ings = recipe.ingredients || []
+  const coco = ings.find(i => i.oil === '椰子油')
+  if (coco && coco.drops) {
+    const totalDrops = ings.reduce((s, i) => s + (i.drops || 0), 0)
+    const ml = totalDrops / 18.6
+    if (ml <= 2) return '单次'
+    return `${Math.round(ml)}ml`
+  }
+  let totalMl = 0
+  let hasProduct = false
+  for (const ing of ings) {
+    if (!oils.isPortionUnit(ing.oil)) continue
+    hasProduct = true
+    totalMl += ing.drops || 0
+  }
+  if (hasProduct && totalMl > 0) return `${Math.round(totalMl)}ml`
+  return ''
+}
+
 onMounted(async () => {
   if (!auth.isBusiness && !auth.isAdmin) {
     router.replace('/projects')