feat: 配方查询支持按精油名搜索

输入精油中文名/英文名会返回含该精油的所有配方。
中文查询 ≥2 字才匹配精油，避免「草」这样的单字噪音。

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

frontend/src/views/RecipeSearch.vue

@@ -312,7 +312,7 @@ function expandQuery(q) {
   return terms
 }
 
-// Search results: exact matches (query in recipe name or tags, NOT oil names to avoid noise like 西班牙牛至)
+// Search results: matches in recipe name, tags, oil names (zh + en)
 const exactResults = computed(() => {
   if (!searchQuery.value.trim()) return []
   const q = searchQuery.value.trim().toLowerCase()
@@ -322,9 +322,10 @@ const exactResults = computed(() => {
     const nameMatch = r.name.toLowerCase().includes(q)
     const enNameMatch = isEn && (r.en_name || '').toLowerCase().includes(q)
     const oilEnMatch = isEn && r.ingredients.some(ing => (oilEn(ing.oil) || '').toLowerCase().includes(q))
+    const oilZhMatch = q.length >= 2 && r.ingredients.some(ing => ing.oil.toLowerCase().includes(q))
     const visibleTags = auth.canEdit ? (r.tags || []) : (r.tags || []).filter(t => !EDITOR_ONLY_TAGS.includes(t))
     const tagMatch = visibleTags.some(t => t.toLowerCase().includes(q))
-    return nameMatch || enNameMatch || oilEnMatch || tagMatch
+    return nameMatch || enNameMatch || oilEnMatch || oilZhMatch || tagMatch
   }).sort((a, b) => a.name.localeCompare(b.name, 'zh'))
 })