feat: 问卷支持暂存功能，打开时自动恢复上次填写内容

frontend/src/components/SurveyModal.tsx

@@ -1,5 +1,5 @@
-import { useState, useMemo } from 'react'
-import { Star, ChevronDown, ChevronRight, Check, Search, ClipboardList, Send } from 'lucide-react'
+import { useState, useMemo, useEffect, useCallback } from 'react'
+import { Star, ChevronDown, ChevronRight, Check, Search, ClipboardList, Send, Save, RotateCcw } from 'lucide-react'
 import Modal from './ui/Modal'
 import { toast } from 'sonner'
 import api from '../lib/api'
@@ -11,11 +11,56 @@ interface FeatureScore {
   remark: string
 }
 
+const STORAGE_KEY = 'survey-draft'
+
 export default function SurveyModal({ open, onClose }: { open: boolean; onClose: () => void }) {
   const [expandedPage, setExpandedPage] = useState<number | null>(1)
   const [scores, setScores] = useState<Record<string, FeatureScore>>({})
   const [searchQuery, setSearchQuery] = useState('')
   const [submitting, setSubmitting] = useState(false)
+  const [savedAt, setSavedAt] = useState<string | null>(null)
+
+  /** 从 localStorage 恢复暂存数据 */
+  const loadDraft = useCallback(() => {
+    try {
+      const raw = localStorage.getItem(STORAGE_KEY)
+      if (raw) {
+        const data = JSON.parse(raw)
+        if (data.scores && typeof data.scores === 'object') {
+          setScores(data.scores)
+          setSavedAt(data.savedAt || null)
+        }
+      }
+    } catch {
+      // 忽略解析错误
+    }
+  }, [])
+
+  /** 暂存到 localStorage */
+  const saveDraft = useCallback(() => {
+    const hasData = Object.values(scores).some(s => s.score > 0 || s.useful || s.remark)
+    if (!hasData) {
+      toast.info('暂无可保存的填写内容')
+      return
+    }
+    const now = new Date().toISOString()
+    localStorage.setItem(STORAGE_KEY, JSON.stringify({ scores, savedAt: now }))
+    setSavedAt(now)
+    toast.success('已暂存填写内容，下次打开可恢复')
+  }, [scores])
+
+  /** 清空暂存 */
+  const clearDraft = useCallback(() => {
+    localStorage.removeItem(STORAGE_KEY)
+    setScores({})
+    setSavedAt(null)
+    toast.info('已清空所有填写内容')
+  }, [])
+
+  /** 打开时恢复暂存 */
+  useEffect(() => {
+    if (open) loadDraft()
+  }, [open, loadDraft])
 
   const setScore = (id: string, score: number) => {
     setScores(prev => ({
@@ -61,10 +106,14 @@ export default function SurveyModal({ open, onClose }: { open: boolean; onClose:
     try {
       await api.post('/survey/submit', { items })
       toast.success(`已提交 ${items.length} 项评分，感谢您的反馈！`)
+      localStorage.removeItem(STORAGE_KEY)
+      setSavedAt(null)
       onClose()
     } catch {
       localStorage.setItem('survey-results', JSON.stringify({ items, submittedAt: new Date().toISOString() }))
       toast.success(`已保存 ${items.length} 项评分到本地`)
+      localStorage.removeItem(STORAGE_KEY)
+      setSavedAt(null)
       onClose()
     } finally {
       setSubmitting(false)
@@ -168,13 +217,26 @@ export default function SurveyModal({ open, onClose }: { open: boolean; onClose:
 
       {/* 底部提交 */}
       <div className="border-t border-gray-200 px-4 py-3 flex items-center justify-between">
-        <span className="text-xs text-gray-500">已评分 {ratedCount} / {totalFeatures} 项</span>
+        <div className="flex flex-col gap-0.5">
+          <span className="text-xs text-gray-500">已评分 {ratedCount} / {totalFeatures} 项</span>
+          {savedAt && <span className="text-xs text-gray-400">上次暂存：{new Date(savedAt).toLocaleString('zh-CN')}</span>}
+        </div>
         <div className="flex gap-2">
           <button
-            onClick={onClose}
-            className="px-3 py-1.5 text-sm text-gray-600 border border-gray-200 rounded-md hover:bg-gray-50"
+            onClick={clearDraft}
+            disabled={ratedCount === 0 && !savedAt}
+            className="px-3 py-1.5 text-sm text-gray-500 border border-gray-200 rounded-md hover:bg-gray-50 disabled:opacity-50 flex items-center gap-1"
           >
-            关闭
+            <RotateCcw className="w-3.5 h-3.5" />
+            清空
+          </button>
+          <button
+            onClick={saveDraft}
+            disabled={ratedCount === 0}
+            className="px-3 py-1.5 text-sm text-gray-600 border border-gray-200 rounded-md hover:bg-gray-50 disabled:opacity-50 flex items-center gap-1"
+          >
+            <Save className="w-3.5 h-3.5" />
+            暂存
           </button>
           <button
             onClick={handleSubmit}