feat: 配方volume字段存储编辑器选择的容量

- 后端: recipes表新增volume列，API返回/保存volume
- 前端: 保存时发送formVolume，编辑时优先用stored volume
- 容量显示优先级: stored volume > 椰子油计算 > 产品ml求和
- 修复编辑器容量选择保存后不生效的bug

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

frontend/src/components/RecipeCard.vue

@@ -48,6 +48,15 @@ const priceInfo = computed(() => oilsStore.fmtCostWithRetail(props.recipe.ingred
 const isFav = computed(() => recipesStore.isFavorite(props.recipe))
 
 const volumeLabel = computed(() => {
+  // Priority 1: stored volume from editor selection
+  const vol = props.recipe.volume
+  if (vol) {
+    if (vol === 'single') return '单次'
+    if (vol === 'custom') return ''
+    if (/^\d+$/.test(vol)) return `${vol}ml`
+    return vol
+  }
+  // Priority 2: calculate from ingredients
   const ings = props.recipe.ingredients || []
   const coco = ings.find(i => i.oil === '椰子油')
   if (coco && coco.drops) {
@@ -56,7 +65,7 @@ const volumeLabel = computed(() => {
     if (ml <= 2) return '单次'
     return `${Math.round(ml)}ml`
   }
-  // Non-coconut: sum all portion products as ml
+  // Priority 3: sum portion products as ml
   let totalMl = 0
   let hasProduct = false
   for (const ing of ings) {

frontend/src/views/RecipeManager.vue

@@ -171,7 +171,7 @@
           />
           <div class="row-info" @click="editRecipe(r)">
             <span class="row-name">{{ r.name }}</span>
-            <span v-if="getVolumeLabel(r.ingredients)" class="row-volume">{{ getVolumeLabel(r.ingredients) }}</span>
+            <span v-if="getVolumeLabel(r.ingredients, r.volume)" class="row-volume">{{ getVolumeLabel(r.ingredients, r.volume) }}</span>
             <span class="row-tags">
               <span v-for="t in [...(r.tags || [])].sort((a,b)=>a.localeCompare(b,'zh'))" :key="t" class="mini-tag">{{ t }}</span>
             </span>
@@ -777,17 +777,25 @@ function editRecipe(recipe) {
   const coco = ings.find(i => i.oil === '椰子油')
   if (coco) {
     formCocoRow.value = { ...coco, _search: '椰子油', _open: false }
-    // Guess volume from total drops
-    const eoDrops = ings.filter(i => i.oil && i.oil !== '椰子油').reduce((s, i) => s + (i.drops || 0), 0)
-    const totalDrops = eoDrops + coco.drops
-    const ml = totalDrops / DROPS_PER_ML
-    if (ml <= 2) formVolume.value = 'single'
-    else if (Math.abs(ml - 5) < 1.5) formVolume.value = '5'
-    else if (Math.abs(ml - 10) < 2.5) formVolume.value = '10'
-    else if (Math.abs(ml - 15) < 2.5) formVolume.value = '15'
-    else if (Math.abs(ml - 20) < 3) formVolume.value = '20'
-    else if (Math.abs(ml - 30) < 6) formVolume.value = '30'
-    else { formVolume.value = 'custom'; formCustomVolume.value = Math.round(ml) }
+    // Use stored volume if available, otherwise guess from drops
+    if (recipe.volume) {
+      formVolume.value = recipe.volume
+      if (recipe.volume === 'custom') {
+        const totalDrops = ings.reduce((s, i) => s + (i.drops || 0), 0)
+        formCustomVolume.value = Math.round(totalDrops / DROPS_PER_ML)
+      }
+    } else {
+      const eoDrops = ings.filter(i => i.oil && i.oil !== '椰子油').reduce((s, i) => s + (i.drops || 0), 0)
+      const totalDrops = eoDrops + coco.drops
+      const ml = totalDrops / DROPS_PER_ML
+      if (ml <= 2) formVolume.value = 'single'
+      else if (Math.abs(ml - 5) < 1.5) formVolume.value = '5'
+      else if (Math.abs(ml - 10) < 2.5) formVolume.value = '10'
+      else if (Math.abs(ml - 15) < 2.5) formVolume.value = '15'
+      else if (Math.abs(ml - 20) < 3) formVolume.value = '20'
+      else if (Math.abs(ml - 30) < 6) formVolume.value = '30'
+      else { formVolume.value = 'custom'; formCustomVolume.value = Math.round(ml) }
+    }
     // Guess dilution
     if (eoDrops > 0 && coco.drops > 0) {
       const ratio = Math.round(coco.drops / eoDrops)
@@ -1091,6 +1099,7 @@ async function saveCurrentRecipe() {
       ingredients: mappedIngs,
       note: formNote.value,
       tags: formTags.value,
+      volume: formVolume.value || '',
     }
     try {
       await recipeStore.saveRecipe(payload)
@@ -1455,7 +1464,15 @@ function openRecipeDetail(recipe) {
   if (idx >= 0) previewRecipeIndex.value = idx
 }
 
-function getVolumeLabel(ingredients) {
+function getVolumeLabel(ingredients, volume) {
+  // Priority 1: stored volume
+  if (volume) {
+    if (volume === 'single') return '单次'
+    if (volume === 'custom') return ''
+    if (/^\d+$/.test(volume)) return `${volume}ml`
+    return volume
+  }
+  // Priority 2: calculate from ingredients
   const ings = ingredients || []
   const coco = ings.find(i => i.oil === '椰子油')
   if (coco && coco.drops) {
@@ -1464,7 +1481,7 @@ function getVolumeLabel(ingredients) {
     if (ml <= 2) return '单次'
     return `${Math.round(ml)}ml`
   }
-  // Non-coconut: sum portion products, mixed units all convert to ml
+  // Priority 3: sum portion products as ml
   let totalMl = 0
   let hasProduct = false
   for (const ing of ings) {