feat(payouts): admin review, PayoutProvider interface, and ledger audit trail

backend/app/services/payout.py

@@ -15,7 +15,9 @@ from sqlalchemy import select
 from sqlalchemy.ext.asyncio import AsyncSession
 
 from app.models.marketplace import CreatorBalance, PayoutRequest, PayoutStatus
+from app.models.wallet import Transaction, TransactionType
 from app.services.purchase import PurchaseService
+from app.services.wallet import WalletService
 
 logger = logging.getLogger(__name__)
 
@@ -158,6 +160,24 @@ class PayoutService:
         payout.reviewed_by = reviewer_id
         payout.reviewed_at = now
 
+        # Record immutable ledger audit row
+        wallet = await WalletService.get_or_create_wallet(db, payout.creator_id, for_update=True)
+        tx = Transaction(
+            wallet_id=wallet.id,
+            type=TransactionType.payout,
+            amount=-payout.amount,
+            balance_after=wallet.balance,
+            reference_type="payout_request",
+            reference_id=str(payout.id),
+            idempotency_key=f"payout-audit-{payout.id}",
+            metadata_json={
+                "provider_ref": provider_ref,
+                "reviewed_by": reviewer_id,
+                "external_ref": payout.external_ref,
+            },
+        )
+        db.add(tx)
+
         await db.commit()
         await db.refresh(payout)
         return payout