完善生图5.0的功能

backend/internal/billing/ledger.go

@@ -10,8 +10,9 @@ import (
 )
 
 var (
-	ErrInsufficientBalance = errors.New("insufficient billing balance")
-	ErrIdempotencyConflict = errors.New("billing idempotency conflict")
+	ErrInsufficientBalance     = errors.New("insufficient billing balance")
+	ErrIdempotencyConflict     = errors.New("billing idempotency conflict")
+	ErrOrganizationUnavailable = errors.New("billing organization is unavailable")
 )
 
 type WalletPostParams struct {