feat(settings): Routstr AI budget panel — the integration's missing switch

The Routstr backend (Cashu-paid inference fallback, shipped 1.7.127) was
fully wired but permanently dormant: its D-05 gate requires an
operator-set sats allowance and nothing in the UI ever called
assistant.budget-get/set — default 0 meant never selected. New Settings
panel (below AI Data Access): allowance/spent/remaining, set-allowance
with 0-disables semantics, enabled/off badge. Backend untouched.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

neode-ui/src/views/settings/SystemSection.vue

@@ -3,6 +3,7 @@ import InterfaceModeSection from '@/views/settings/InterfaceModeSection.vue'
 import KioskDisplaySection from '@/views/settings/KioskDisplaySection.vue'
 import ClaudeAuthSection from '@/views/settings/ClaudeAuthSection.vue'
 import AIDataAccessSection from '@/views/settings/AIDataAccessSection.vue'
+import RoutstrBudgetSection from '@/views/settings/RoutstrBudgetSection.vue'
 import WebhookSection from '@/views/settings/WebhookSection.vue'
 import TelemetrySection from '@/views/settings/TelemetrySection.vue'
 import NodeCertificateSection from '@/views/settings/NodeCertificateSection.vue'
@@ -16,6 +17,7 @@ import SystemDangerZone from '@/views/settings/SystemDangerZone.vue'
   <KioskDisplaySection />
   <ClaudeAuthSection />
   <AIDataAccessSection />
+  <RoutstrBudgetSection />
   <WebhookSection />
   <TelemetrySection />
   <NodeCertificateSection />