🎫 feat: Enhance redemption code expiry handling & improve UI responsiveness

Backend
• Introduced `validateExpiredTime` helper in `controller/redemption.go`; reused in both Add & Update endpoints to enforce “expiry time must not be earlier than now”, eliminating duplicated checks
• Removed `RedemptionCodeStatusExpired` constant and all related references – expiry is now determined exclusively by the `expired_time` field for simpler, safer state management
• Simplified `DeleteInvalidRedemptions`: deletes codes that are `used` / `disabled` or `enabled` but already expired, without relying on extra status codes
• Controller no longer mutates `status` when listing or fetching redemption codes; clients derive expiry status from timestamp

Frontend
• Added reusable `isExpired` helper in `RedemptionsTable.js`; leveraged for:
  – status rendering (orange “Expired” tag)
  – action-menu enable/disable logic
  – row styling
• Removed duplicated inline expiry logic, improving readability and performance
• Adjusted toolbar layout: on small screens the “Clear invalid codes” button now wraps onto its own line, while “Add” & “Copy” remain grouped

Result
The codebase is now more maintainable, secure, and performant with no redundant constants, centralized validation, and cleaner UI behaviour across devices.

model/redemption.go

@@ -21,6 +21,7 @@ type Redemption struct {
 	Count        int            `json:"count" gorm:"-:all"` // only for api request
 	UsedUserId   int            `json:"used_user_id"`
 	DeletedAt    gorm.DeletedAt `gorm:"index"`
+	ExpiredTime  int64          `json:"expired_time" gorm:"bigint"` // 过期时间，0 表示不过期
 }
 
 func GetAllRedemptions(startIdx int, num int) (redemptions []*Redemption, total int64, err error) {
@@ -131,6 +132,9 @@ func Redeem(key string, userId int) (quota int, err error) {
 		if redemption.Status != common.RedemptionCodeStatusEnabled {
 			return errors.New("该兑换码已被使用")
 		}
+		if redemption.ExpiredTime != 0 && redemption.ExpiredTime < common.GetTimestamp() {
+			return errors.New("该兑换码已过期")
+		}
 		err = tx.Model(&User{}).Where("id = ?", userId).Update("quota", gorm.Expr("quota + ?", redemption.Quota)).Error
 		if err != nil {
 			return err
@@ -162,7 +166,7 @@ func (redemption *Redemption) SelectUpdate() error {
 // Update Make sure your token's fields is completed, because this will update non-zero values
 func (redemption *Redemption) Update() error {
 	var err error
-	err = DB.Model(redemption).Select("name", "status", "quota", "redeemed_time").Updates(redemption).Error
+	err = DB.Model(redemption).Select("name", "status", "quota", "redeemed_time", "expired_time").Updates(redemption).Error
 	return err
 }
 
@@ -183,3 +187,9 @@ func DeleteRedemptionById(id int) (err error) {
 	}
 	return redemption.Delete()
 }
+
+func DeleteInvalidRedemptions() (int64, error) {
+	now := common.GetTimestamp()
+	result := DB.Where("status IN ? OR (status = ? AND expired_time != 0 AND expired_time < ?)", []int{common.RedemptionCodeStatusUsed, common.RedemptionCodeStatusDisabled}, common.RedemptionCodeStatusEnabled, now).Delete(&Redemption{})
+	return result.RowsAffected, result.Error
+}