fix(wallet): stop double-deducting balance on outgoing payments

The wallet WebSocket handler assumed LNbits sends the PRE-payment balance
for outgoing payments and subtracted the amount again. LNbits actually
re-fetches the wallet AFTER the payment settles before emitting the
notification (core payments.py `_send_payment_notification_in_background`
→ "fetch balance again" → notifications.py `send_ws_payment_notification`
→ `wallet.balance`), so `wallet_balance` is already POST-payment for both
directions. The extra subtraction double-deducted: 100 sats, send 10 →
balance showed 80, then a refresh (which reads the authoritative
/api/v1/wallet balance) corrected it to 90.

Use `wallet_balance` as-is for all messages, matching the polling
fallback which already trusts the API balance directly.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/modules/wallet/services/WalletWebSocketService.ts

@@ -231,41 +231,21 @@ export class WalletWebSocketService extends BaseService {
         this.handlePaymentNotification(data.payment)
       }
 
-      // Handle wallet balance update
+      // Handle wallet balance update.
+      // `wallet_balance` is authoritative and already POST-payment for BOTH
+      // directions: LNbits re-fetches the wallet AFTER the payment settles
+      // before emitting the notification (core services/payments.py
+      // `_send_payment_notification_in_background` → "fetch balance again" →
+      // services/notifications.py `send_ws_payment_notification` →
+      // `wallet.balance`). Use it as-is. The previous code subtracted the
+      // outgoing amount on top, double-deducting (100 → send 10 → showed 80,
+      // refresh corrected to 90).
       if (data.wallet_balance !== undefined) {
-        console.log('WalletWebSocketService: Processing balance update', {
-          newBalance: data.wallet_balance,
+        console.log('WalletWebSocketService: Updating balance to', data.wallet_balance, 'sats', {
           hasPayment: !!data.payment,
           paymentAmount: data.payment?.amount
         })
-
-        let finalBalance = data.wallet_balance
-
-        // For outgoing payments, LNbits sends pre-payment balance, so we need to adjust
-        // For incoming payments, LNbits sends post-payment balance, so use as-is
-        if (data.payment && data.payment.amount < 0) {
-          // Outgoing payment - subtract the payment amount from the balance
-          const paymentSats = Math.abs(data.payment.amount) / 1000
-          finalBalance = data.wallet_balance - paymentSats
-          console.log('WalletWebSocketService: Adjusting balance for outgoing payment', {
-            originalBalance: data.wallet_balance,
-            paymentSats: paymentSats,
-            finalBalance: finalBalance
-          })
-        } else if (data.payment && data.payment.amount > 0) {
-          // Incoming payment - use balance as-is (already post-payment)
-          console.log('WalletWebSocketService: Using balance as-is for incoming payment', {
-            balance: data.wallet_balance
-          })
-        } else {
-          // No payment in message - use balance as-is
-          console.log('WalletWebSocketService: Using balance as-is (no payment)', {
-            balance: data.wallet_balance
-          })
-        }
-
-        console.log('WalletWebSocketService: Updating balance to', finalBalance, 'sats')
-        this.updateWalletBalance(finalBalance)
+        this.updateWalletBalance(data.wallet_balance)
       }
 
     } catch (error) {