feat(user): 支持后台调整等级并限制极品专区可见性

backend/internal/modules/order/service.go

@@ -10,6 +10,7 @@ var (
 	ErrInvalidRentHours            = errors.New("invalid rent hours")
 	ErrListingUnavailable          = errors.New("listing unavailable")
 	ErrCannotRentOwnListing        = errors.New("cannot rent own listing")
+	ErrPremiumLevelRequired        = errors.New("platinum level required for premium listing")
 	ErrInsufficientBalance         = errors.New("insufficient balance")
 	ErrOrderCannotPay              = errors.New("order cannot pay")
 	ErrChannelPaymentRequired      = errors.New("channel payment required")