fix(fin): 激活配置并发行锁保护 FIN-03

- commission_withdrawal_setting/service.go: 激活事务内首步加 FOR UPDATE 行锁，防止并发时出现多条 is_active=true
- wechat_config_store.go: ActivateInTx 激活前同样加行锁保护

internal/service/commission_withdrawal_setting/service.go

@@ -11,6 +11,7 @@ import (
 	"github.com/break/junhong_cmp_fiber/pkg/errors"
 	"github.com/break/junhong_cmp_fiber/pkg/middleware"
 	"gorm.io/gorm"
+	"gorm.io/gorm/clause"
 )
 
 type Service struct {
@@ -47,6 +48,12 @@ func (s *Service) Create(ctx context.Context, req *dto.CreateWithdrawalSettingRe
 	setting.Updater = currentUserID
 
 	err := s.db.Transaction(func(tx *gorm.DB) error {
+		// 先锁定当前活跃记录，防止并发激活导致多条 is_active=true
+		var current model.CommissionWithdrawalSetting
+		tx.WithContext(ctx).Clauses(clause.Locking{Strength: "UPDATE"}).
+			Where("is_active = ?", true).
+			First(&current)
+
 		if err := s.commissionWithdrawalSettingStore.DeactivateCurrentWithTx(ctx, tx); err != nil {
 			return errors.Wrap(errors.CodeInternalError, err, "失效旧配置失败")
 		}

internal/store/postgres/wechat_config_store.go

@@ -7,6 +7,7 @@ import (
 	"github.com/break/junhong_cmp_fiber/internal/store"
 	"github.com/redis/go-redis/v9"
 	"gorm.io/gorm"
+	"gorm.io/gorm/clause"
 )
 
 // WechatConfigStore 微信参数配置数据访问层
@@ -100,6 +101,12 @@ func (s *WechatConfigStore) GetActive(ctx context.Context) (*model.WechatConfig,
 
 // ActivateInTx 在事务内激活指定配置（先停用所有，再激活指定记录）
 func (s *WechatConfigStore) ActivateInTx(ctx context.Context, tx *gorm.DB, id uint) error {
+	// 先锁定当前活跃记录，防止并发激活导致多条 is_active=true
+	var current model.WechatConfig
+	tx.WithContext(ctx).Clauses(clause.Locking{Strength: "UPDATE"}).
+		Where("is_active = ?", true).
+		First(&current)
+
 	// 先停用所有激活的配置
 	if err := tx.WithContext(ctx).Model(&model.WechatConfig{}).
 		Where("is_active = ?", true).