feat: 导出Excel多sheet，按标签分页

- 文件名：精油配方YYYY-MM-DD.xlsx
- 第一个sheet"全部"包含所有配方
- 每个标签一个单独的sheet
- 使用SheetJS生成真正的xlsx格式

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

frontend/src/views/RecipeManager.vue

@@ -1109,25 +1109,36 @@ async function rejectRecipe(recipe) {
   }
 }
 
-function exportExcel() {
+async function exportExcel() {
   const recipes = recipeStore.recipes
   if (!recipes.length) { ui.showToast('没有配方可导出'); return }
-  // BOM for UTF-8 Excel compatibility
-  let csv = '\uFEFF配方名称,标签,精油成分,滴数,成本\n'
-  for (const r of recipes) {
-    const tags = (r.tags || []).join('/')
-    const ings = r.ingredients.map(i => i.oil).join('、')
-    const drops = r.ingredients.map(i => `${i.oil}${i.drops}滴`).join('、')
-    const cost = oils.fmtPrice(oils.calcCost(r.ingredients))
-    csv += `"${r.name}","${tags}","${ings}","${drops}","${cost}"\n`
+  const XLSX = (await import('xlsx')).default || await import('xlsx')
+
+  function recipesToRows(list) {
+    return list.map(r => ({
+      '配方名称': r.name,
+      '标签': (r.tags || []).join('/'),
+      '精油成分': r.ingredients.map(i => `${i.oil}${i.drops}滴`).join('、'),
+      '成本': oils.fmtPrice(oils.calcCost(r.ingredients)),
+      '备注': r.note || '',
+    }))
   }
-  const blob = new Blob([csv], { type: 'text/csv;charset=utf-8' })
-  const url = URL.createObjectURL(blob)
-  const a = document.createElement('a')
-  a.href = url
-  a.download = '配方导出.csv'
-  a.click()
-  URL.revokeObjectURL(url)
+
+  const wb = XLSX.utils.book_new()
+  // Sheet 1: 全部
+  XLSX.utils.book_append_sheet(wb, XLSX.utils.json_to_sheet(recipesToRows(recipes)), '全部')
+  // Per tag sheets
+  const allTags = [...new Set(recipes.flatMap(r => r.tags || []))].sort((a, b) => a.localeCompare(b, 'zh'))
+  for (const tag of allTags) {
+    const tagged = recipes.filter(r => r.tags && r.tags.includes(tag))
+    if (tagged.length) {
+      const name = tag.substring(0, 31) // Excel sheet name max 31 chars
+      XLSX.utils.book_append_sheet(wb, XLSX.utils.json_to_sheet(recipesToRows(tagged)), name)
+    }
+  }
+
+  const today = new Date().toISOString().slice(0, 10)
+  XLSX.writeFile(wb, `精油配方${today}.xlsx`)
   ui.showToast('导出成功')
 }