feat(demo): app launch UIs, "No demo" gating, onboarding skip, 12 nodes

App launching (DEMO):
- resolveAppUrl routes every app to its demo target: mock UIs for Bitcoin Core,
  ElectrumX, Fedimint (served by the backend), IndeeHub → iframe indee.tx1138.com,
  Mempool → mempool.space/testnet (new tab); all others → a generic "Demo preview"
  notice page.
- Non-demoable apps show a disabled "No demo" install button (marketplace details,
  app grid, featured apps).

Onboarding:
- Demo treats the visitor as fully set up so the onboarding WIZARD (seed/identity)
  is never forced; the welcome intro still replays per day. Intro CTA goes straight
  to login; wizard entry points + login restart-onboarding link hidden in demo.

Network:
- federation.list-nodes now returns 12 trusted/federated nodes (9 trusted, 3
  observer); transport.peers already at 5.

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

neode-ui/src/views/discover/AppGrid.vue

@@ -116,6 +116,12 @@
               Checking...
             </span>
           </span>
+          <!-- Demo: app not demoable -->
+          <button
+            v-else-if="IS_DEMO && !isInstalled(app.id) && !isDemoApp(app.id)"
+            disabled
+            class="flex-1 px-4 py-2 bg-white/10 rounded-lg text-white/40 text-sm font-medium cursor-not-allowed"
+          >No demo</button>
           <!-- Install button -->
           <button
             v-else-if="!isInstalled(app.id) && (app.source === 'local' || app.dockerImage)"
@@ -158,6 +164,7 @@
 <script setup lang="ts">
 import type { MarketplaceApp } from './types'
 import { handleImageError } from '@/views/apps/appsConfig'
+import { IS_DEMO, isDemoApp } from '@/composables/useDemoIntro'
 
 defineProps<{
   filteredApps: MarketplaceApp[]

neode-ui/src/views/discover/FeaturedApps.vue

@@ -74,6 +74,11 @@
             </svg>
             Checking...
           </button>
+          <button
+            v-else-if="IS_DEMO && !isInstalled(app.id) && !isDemoApp(app.id)"
+            disabled
+            class="glass-button glass-button-sm rounded-lg text-sm font-medium opacity-50 cursor-not-allowed"
+          >No demo</button>
           <button
             v-else-if="!isInstalled(app.id) && app.dockerImage"
             data-controller-install-btn
@@ -99,6 +104,7 @@
 <script setup lang="ts">
 import type { FeaturedApp, MarketplaceApp } from './types'
 import { handleImageError } from '@/views/apps/appsConfig'
+import { IS_DEMO, isDemoApp } from '@/composables/useDemoIntro'
 
 defineProps<{
   featuredApps: FeaturedApp[]