feat(wallet): offer to install a Lightning node instead of failing an invoice

Creating a Lightning invoice with no Lightning implementation installed failed
at the RPC layer — lnd.createinvoice returned connection-refused and the
Receive screen rendered it as a red error. That reads as the wallet being
broken when the node simply has no Lightning node installed yet.

useLightningRequired() gates the three invoice paths (wallet Receive, the Web5
send/receive sheet, and the app launcher's paywall — both arms there, since
paying an invoice needs a node as much as minting one). With none installed it
raises a modal offering to install one and the caller bails without surfacing
an error at all.

The modal lists the choice rather than assuming LND: LND installs today, Core
Lightning is listed greyed as "Coming soon" so the platform doesn't read as
LND-only. When CLN ships it is two lines — flip `available` and add the id to
LIGHTNING_NODE_APP_IDS.

Detection is install state, NOT reachability, deliberately: an installed node
that is merely stopped or still starting is a different problem ("start it")
and must not be answered with "install a Lightning node".

Also fixes the credentials modal, which painted its own rgba(8,10,18,.98)
navy card instead of the house glass-card — it read as blue against every
other modal. It existed twice (Apps.vue and apps/AppIconGrid.vue); both now
use BaseModal, so they also inherit Esc/focus handling, body scroll lock and
the standard pinned-header/footer scroll contract they were missing. Dead
panel CSS removed from both.

Verified: 4 new tests; full suite 103 files / 826 tests green; npm run build
clean with the new strings present in the built bundle.

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

neode-ui/src/components/ReceiveBitcoinModal.vue

@@ -91,8 +91,10 @@ import { useI18n } from 'vue-i18n'
 import { rpcClient } from '@/api/rpc-client'
 import BaseModal from '@/components/BaseModal.vue'
 import { explainReceiveAddressFailure } from '@/utils/bitcoinReceive'
+import { useLightningRequired } from '@/composables/useLightningRequired'
 
 const { t } = useI18n()
+const lightning = useLightningRequired()
 
 const props = defineProps<{
   show: boolean
@@ -154,6 +156,10 @@ async function receive() {
   error.value = ''
   try {
     if (receiveMethod.value === 'lightning') {
+      // 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 (!invoiceAmount.value) { error.value = t('receiveBitcoin.enterAnAmount'); return }
       const res = await rpcClient.call<{ payment_request: string }>({
         method: 'lnd.createinvoice',