fix(ui): replace native confirm() dialogs with the global in-app modal

window.confirm blocks the JS event loop, which froze companion remote
input while open — the remote user could raise the mesh "Clear" prompt
(or reboot / backup-delete / uninstall confirms) and then never dismiss
it, because the synthetic events that would dismiss it queue behind the
dialog itself.

New promise-based appConfirm() (useAppConfirm.ts) + one AppConfirmModal
mounted globally in App.vue, built on BaseModal (Teleport-to-body,
full-viewport backdrop, glass card — the canonical modal contract). All
six native confirm() call sites migrated: mesh clear-all, mesh message
delete, dashboard reboot, backup delete, backup USB copy, app uninstall.

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

neode-ui/src/views/Dashboard.vue

@@ -119,6 +119,7 @@ import { computed, ref, watch, onMounted, onBeforeUnmount } from 'vue'
 import { useRouter, useRoute } from 'vue-router'
 import { useAppStore } from '../stores/app'
 import { useAppLauncherStore } from '../stores/appLauncher'
+import { appConfirm } from '@/composables/useAppConfirm'
 import AppSession from '@/views/AppSession.vue'
 import { useLoginTransitionStore } from '../stores/loginTransition'
 import { playDashboardLoadOomph } from '@/composables/useLoginSounds'
@@ -376,9 +377,10 @@ function handleKioskShortcuts(e: KeyboardEvent) {
       router.push('/dashboard')
     } else if (e.key === 'Q' || e.key === 'q') {
       e.preventDefault()
-      if (confirm('Reboot the server?')) {
+      appConfirm({ title: 'Reboot', message: 'Reboot the server?', confirmLabel: 'Reboot', danger: true }).then((ok) => {
+        if (!ok) return
         fetch('/rpc/', { method: 'POST', headers: { 'Content-Type': 'application/json' }, body: JSON.stringify({ method: 'system.reboot' }) }).catch(() => {})
-      }
+      })
     }
   }
 }