fix: 精油编辑统一保存到 DB + 导出 Excel 增加功效列

- 新增 oil_cards 表，持久化知识卡片（功效/用法/方法/注意/emoji）
- POST /api/oils 扩展接受 card_* 字段，在同一事务里 upsert oil_cards
- GET /api/oil-cards 返回全部卡片
- 前端 getOilCard 优先查 DB，再 fallback 静态表
- saveEditOil 统一走 saveOil，不再分两套保存
- 精油价目 Excel 导出增加「功效」列
- 首次部署自动从静态 OIL_CARDS 播种到 oil_cards 表

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

frontend/src/composables/useOilCards.js

@@ -1,5 +1,6 @@
 // Oil knowledge cards - usage guides for common essential oils
 // Ported from original vanilla JS implementation
+import { useOilsStore } from '../stores/oils'
 
 export const OIL_CARDS = {
   '野橘': { emoji: '🍊', en: 'Wild Orange', effects: '安抚镇静、驱散负能量、紧张情绪和压力\n抗氧化、消炎、抗病毒、增强免疫\n提振食欲，刺激胆汁分泌，促进消化\n促进循环', usage: '日常香薰，提振情绪、舒压，营造愉悦氛围\n饮水加入 1至2 滴，护肝抗病毒\n泡澡时滴 3至4 滴，消除疲劳，放松身心\n扫地、拖地时加入 3至5 滴，清新空气\n涂抹腹部促进消化\n涂抹肝区帮助肝脏排毒\n口腔溃疡时加入水中漱口', method: '🔹香薰 ｜ 🔸内用 ｜ 🔺涂抹', caution: '轻微光敏，白天涂抹注意防晒' },
@@ -33,6 +34,17 @@ export const OIL_CARD_ALIAS = {
 }
 
 export function getOilCard(name) {
+  // Check DB-persisted cards first (via store)
+  try {
+    const store = useOilsStore()
+    if (store.oilCards[name]) return store.oilCards[name]
+    // Check alias in store too
+    const aliased = OIL_CARD_ALIAS[name]
+    if (aliased && store.oilCards[aliased]) return store.oilCards[aliased]
+  } catch {
+    // Store may not be initialized yet, fall through to static data
+  }
+  // Fall back to static OIL_CARDS
   if (OIL_CARDS[name]) return OIL_CARDS[name]
   if (OIL_CARD_ALIAS[name] && OIL_CARDS[OIL_CARD_ALIAS[name]]) return OIL_CARDS[OIL_CARD_ALIAS[name]]
   const base = name.replace(/呵护$/, '')