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/components/AppLauncherOverlay.vue

@@ -525,10 +525,10 @@ async function approvePayment() {
       receipt = { method: 'ecash', token: res.token, amount_sats: res.amount_sats }
     } else if (method === 'lightning') {
       if (pay.invoice) {
-        const res = await rpcClient.call<{ payment_hash: string; amount_sats: number }>({
-          method: 'lnd.payinvoice',
-          params: { payment_request: pay.invoice },
-        })
+        // Tracked to a real terminal state — slow routing is not a failure.
+        const res = await rpcClient.payLightningInvoice({ payment_request: pay.invoice })
+        if (res.status === 'failed') throw new Error(res.failure_reason || 'Payment failed')
+        if (res.status === 'pending') throw new Error('Payment is still settling — check your wallet transactions before retrying.')
         receipt = { method: 'lightning', payment_hash: res.payment_hash, amount_sats: res.amount_sats }
       } else {
         // Create and immediately return an invoice for the requester to display