fix(lightning): never report a slow in-flight payment as failed

Slow multi-hop payments (>15s routing) surfaced as "Payment failed"
while LND settled them in the background: the shared LND REST client's
15s total timeout aborted the synchronous /v1/channels/transactions
wait, and every UI path treated that abort as a definitive failure. The
payment then succeeded anyway and only appeared in history on the next
background poll.

Backend: lnd.payinvoice now decodes the invoice up front for its payment
hash, pays on a dedicated 120s client, and answers status:"pending" with
the hash (never an error) when the wait elapses after the payment was
handed to LND — only a pre-connect failure is still a hard error. New
lnd.paymentstatus RPC reports succeeded/failed/in_flight (with humanized
failure reasons) from /v1/payments.

Frontend: new rpcClient.payLightningInvoice() pays then polls
lnd.paymentstatus to a real terminal state (3s interval, up to 2 min);
all five call sites (send modal, scan modal, web5 unified send, peer-file
purchase, app-launcher payments) migrated. Failure is only shown when LND
itself declares FAILED; a still-settling payment shows an in-flight state
and success fires the transaction refresh.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

neode-ui/src/views/web5/Web5SendReceiveModals.vue

@@ -291,10 +291,10 @@ async function unifiedSend() {
         unifiedSendError.value = t('web5.pasteInvoice')
         return
       }
-      const res = await rpcClient.call<{ payment_hash: string; amount_sats: number }>({
-        method: 'lnd.payinvoice',
-        params: { payment_request: unifiedSendDest.value.trim() },
-      })
+      // Waits out slow multi-hop routing and only reports failure when LND
+      // itself declares the payment failed — never on a timeout.
+      const res = await rpcClient.payLightningInvoice({ payment_request: unifiedSendDest.value.trim() })
+      if (res.status === 'failed') throw new Error(res.failure_reason || 'Payment failed')
       sendResultHash.value = res.payment_hash
     } else {
       if (!unifiedSendDest.value.trim()) {