Add invoice payment management.

Co-authored-by: Cursor <cursoragent@cursor.com>

backend/src/common/enums.ts

@@ -111,6 +111,30 @@ export enum TransactionType {
   CHARGE = 'charge',       // Top-up / deposit
   DEDUCTION = 'deduction', // Payment for service
   REFUND = 'refund',       // Refund
+  GATEWAY_PAYMENT = 'gateway_payment', // Direct payment through a gateway
+}
+
+export enum InvoiceStatus {
+  DRAFT = 'draft',
+  ISSUED = 'issued',
+  PARTIALLY_PAID = 'partially_paid',
+  PAID = 'paid',
+  VOID = 'void',
+  FAILED = 'failed',
+}
+
+export enum PaymentMethod {
+  WALLET = 'wallet',
+  GATEWAY = 'gateway',
+  MIXED = 'mixed',
+}
+
+export enum InvoiceReason {
+  DEPLOY = 'deploy',
+  RENEWAL = 'renewal',
+  UPGRADE = 'upgrade',
+  WALLET_TOPUP = 'wallet_topup',
+  MANUAL = 'manual',
 }
 
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