feat: NostrVPN as native system service, Claude API key input, fix duplicate password

- Add NostrVPN as a native systemd service (extracted from container)
- Add VPN status detection for nostr-vpn in backend vpn.rs
- ISO build extracts nvpn binary from container image
- First-boot auto-configures NostrVPN with node's Nostr identity
- Change Claude Auth from login iframe to API key input field
- Remove duplicate ChangePasswordSection from Settings.vue
- FIPS and Routstr remain as installable container apps

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

neode-ui/src/views/Settings.vue

@@ -1,13 +1,11 @@
 <script setup lang="ts">
 import AccountSection from '@/views/settings/AccountSection.vue'
-import ChangePasswordSection from '@/views/settings/ChangePasswordSection.vue'
 import SystemSection from '@/views/settings/SystemSection.vue'
 </script>
 
 <template>
   <div class="pb-6">
     <AccountSection />
-    <ChangePasswordSection />
     <SystemSection />
   </div>
 </template>