fix(wallet): gate lightning on CHANNELS, not just node state

A running LND with zero channels happily mints an invoice — it is simply
unpayable, because nobody has a route in. So the state-only gate let receive
through and handed the user a useless invoice, and let send walk to confirm.
Neither errored, so the funding modal (wired to failures) never fired.

requireLightningReady(direction) now asks lnd.listchannels and checks the
liquidity that actually matters for the attempt: total_inbound to receive,
total_outbound to send. It fails OPEN on an RPC error — a transient blip
should not block a working wallet.

The no-funds mode says plainly that a channel is needed, in the direction's
own terms (inbound vs outbound), and offers both routes: "Open a channel"
straight to the channels screen where the Zeus/Olympus flow is already
prefilled, and "Setup Guide" to the run-lightning-node walkthrough for someone
who wants the whole path explained. Buttons wrap rather than squeeze on
narrow screens.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

neode-ui/src/components/ReceiveBitcoinModal.vue

@@ -156,7 +156,7 @@ async function receive() {
       // No Lightning implementation installed is not an error — it is a
       // missing prerequisite. Raise the install modal instead of letting
       // lnd.createinvoice fail with connection-refused (FED-08 follow-up).
-      if (!lightning.requireLightningNode()) return
+      if (!(await lightning.requireLightningReady('receive'))) return
       if (!invoiceAmount.value) { error.value = t('receiveBitcoin.enterAnAmount'); return }
       const res = await rpcClient.call<{ payment_request: string }>({
         method: 'lnd.createinvoice',