rewrite: 英文名统一读写 oils.en_name，三处同步

核心设计: oils.en_name (DB) 是唯一数据源

读取链路 (全部统一):
- 精油价目: getEnglishName → oilsMeta.enName → oilEn()
- 配方卡片: getCardOilName → oilsMeta.enName → oilEn()
- 翻译编辑器: openTranslationEditor → oilsMeta.enName

写入链路 (全部写同一个字段):
- 精油价目编辑: saveEditOil → oilsStore.saveOil → oils.en_name → loadOils
- 配方卡翻译: applyTranslation → oilsStore.saveOil → oils.en_name → loadOils
- 配方名翻译: applyTranslation → PUT /api/recipes/{id} → recipes.en_name → loadRecipes

保存后:
- await Promise.all([loadOils(), loadRecipes()]) 刷新所有数据
- 下次任何地方渲染都读到最新值
- customOilNameEn 只在编辑器打开期间有效，关闭后丢弃

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

frontend/src/components/RecipeDetailOverlay.vue

@@ -596,41 +596,41 @@ function copyText() {
 }
 
 function openTranslationEditor() {
-  // Pre-populate with existing English names from DB/translation table
+  // Pre-populate from single source of truth: oilsMeta.enName (DB)
   const map = {}
   for (const ing of cardIngredients.value) {
-    const existing = oilsStore.oilsMeta[ing.oil]?.enName || oilEn(ing.oil)
-    if (existing) map[ing.oil] = existing
+    map[ing.oil] = getOilEnglish(ing.oil)
   }
   customOilNameEn.value = map
-  customRecipeNameEn.value = recipe.value.en_name || recipeNameEn(recipe.value.name)
+  customRecipeNameEn.value = recipe.value.en_name || ''
   showTranslationEditor.value = true
 }
 
 async function applyTranslation() {
   showTranslationEditor.value = false
   let saved = 0
+  let failed = 0
 
-  // 1. Save recipe English name (no version check — only updating en_name)
-  if (recipe.value._id && customRecipeNameEn.value) {
+  // 1. Save recipe English name to recipes table
+  if (recipe.value._id && customRecipeNameEn.value.trim()) {
     try {
       await api.put(`/api/recipes/${recipe.value._id}`, {
-        en_name: customRecipeNameEn.value,
+        en_name: customRecipeNameEn.value.trim(),
       })
-      recipe.value.en_name = customRecipeNameEn.value
       saved++
     } catch (e) {
       console.error('Save recipe en_name failed:', e)
+      failed++
     }
   }
 
-  // 2. Save each oil's English name to oils table (syncs with oil reference page)
-  let failed = 0
+  // 2. Save each oil's English name to oils table
+  //    This is THE single source of truth — both oil reference page and recipe card read from here
   for (const [oilName, enName] of Object.entries(customOilNameEn.value)) {
     if (!enName?.trim()) continue
     const meta = oilsStore.oilsMeta[oilName]
     if (!meta) continue
-    if (meta.enName === enName.trim()) continue
+    if (meta.enName === enName.trim()) continue // no change
     try {
       await oilsStore.saveOil(oilName, meta.bottlePrice, meta.dropCount, meta.retailPrice, enName.trim())
       saved++
@@ -640,25 +640,38 @@ async function applyTranslation() {
     }
   }
 
+  // 3. Reload ALL data — this updates oilsMeta.enName and recipe.en_name
+  //    So the next render reads fresh data from the single source
+  await Promise.all([
+    oilsStore.loadOils(),
+    recipesStore.loadRecipes(),
+  ])
+
   if (saved > 0) {
     ui.showToast(`翻译已保存（${saved}项）` + (failed > 0 ? `，${failed}项失败` : ''))
-    // Reload data so next open shows updated names
-    recipesStore.loadRecipes()
-    oilsStore.loadOils()
   } else if (failed > 0) {
     ui.showToast(`保存失败 ${failed} 项`)
   } else {
     ui.showToast('没有修改')
   }
 
+  // Regenerate card image with updated names from store
   cardImageUrl.value = null
   nextTick(() => generateCardImage())
 }
 
 // Override translation getters for card rendering
+function getOilEnglish(name) {
+  return oilsStore.oilsMeta[name]?.enName || oilEn(name) || ''
+}
+
 function getCardOilName(name) {
   if (cardLang.value === 'en') {
-    return customOilNameEn.value[name] || oilsStore.oilsMeta[name]?.enName || oilEn(name) || name
+    // During editing, use customOilNameEn; otherwise read from store (single source of truth)
+    if (showTranslationEditor.value && customOilNameEn.value[name]) {
+      return customOilNameEn.value[name]
+    }
+    return getOilEnglish(name) || name
   }
   return name
 }