fix: share-gain防刷改用shareRecords统计(schema strict丢弃了临时字段)

server/src/routes/aiChat.js

@@ -227,16 +227,12 @@ router.post('/share-gain', userAuthMiddleware, async (req, res) => {
       quota = new AIChatQuota({ openid })
     }
 
-    // [防刷] 每日分享奖励最多3次
-    const today = new Date().toISOString().slice(0, 10)
-    const shareDate = (quota.shareDate || '').toString().slice(0, 10)
-    const shareCount = shareDate === today ? (quota.shareCount || 0) : 0
-    if (shareCount >= 3) {
+    // [防刷] 每日分享奖励最多3次（基于 shareRecords 统计）
+    const dayStart = new Date(); dayStart.setHours(0, 0, 0, 0)
+    const todayShares = (quota.shareRecords || []).filter(r => new Date(r.sharedAt) >= dayStart).length
+    if (todayShares >= 3) {
       return ApiResponse.error(res, '今日分享奖励已领完，明天再来吧', 429)
     }
-    quota.shareDate = new Date()
-    quota.shareCount = shareCount + 1
-    await quota.save()
 
     const remainingQuota = await quota.addQuotaByShare(5)