refactor: 提取 service 层 best-effort 超时常量

- 新增 defaultBETimeout = 5 * time.Second
- 替换 auth/auth_runtime/password_reset/user_service/webhook 中 6 处硬编码 5*time.Second

internal/service/password_reset.go

@@ -299,7 +299,7 @@ func (s *PasswordResetService) doResetPassword(ctx context.Context, user *domain
 	if s.passwordHistoryRepo != nil {
 		// #nosec G118 - 使用带超时的独立 context，防止 DB 写入无限等待
 		go func() { // #nosec G118
-			bgCtx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
+			bgCtx, cancel := context.WithTimeout(context.Background(), defaultBETimeout)
 			defer cancel()
 			_ = s.passwordHistoryRepo.Create(bgCtx, &domain.PasswordHistory{
 				UserID:       user.ID,