add subscription upgrade plan

apps/admin/src/app/dashboard/billing/page.tsx

@@ -119,6 +119,7 @@ interface BillingInvoice {
   creditNotes: CreditNote[]
   refunds: Refund[]
   taxRecords: TaxRecord[]
+  subscriptionUpgradeRequest?: { id: string; status: string } | null
   manualPaymentSubmissions?: Array<{
     id: string
     method: 'BANK_TRANSFER' | 'CHECK'
@@ -980,7 +981,13 @@ export default function AdminBillingPage() {
     setActionError(null)
     setReauthRequired(false)
     try {
-      await api(`/admin/billing/invoices/${selectedInvoice.id}/manual-payments`, {
+      const path = selectedInvoice.invoiceType === 'SUBSCRIPTION_UPGRADE'
+        ? selectedInvoice.subscriptionUpgradeRequest?.id
+          ? `/admin/billing/upgrade-requests/${selectedInvoice.subscriptionUpgradeRequest.id}/approve-payment`
+          : null
+        : `/admin/billing/invoices/${selectedInvoice.id}/manual-payments`
+      if (!path) throw new Error('Upgrade request link is missing for this subscription upgrade invoice.')
+      await api(path, {
         method: 'POST',
         body: JSON.stringify({
           submissionId: submission.id,