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/App.vue

@@ -41,6 +41,10 @@
     <MeshDeviceSetupModal />
     <ExternalExplorerModal />
 
+    <!-- In-app confirm() replacement — native browser dialogs block the JS
+         event loop and freeze companion remote input (see useAppConfirm) -->
+    <AppConfirmModal />
+
     <!-- Nudge to back up the Lightning seed once a wallet exists (any page) -->
     <LndSeedBackupPrompt />
 
@@ -102,6 +106,7 @@ import HelpGuideModal from './components/HelpGuideModal.vue'
 import GlobalAudioPlayer from './components/GlobalAudioPlayer.vue'
 import MeshDeviceSetupModal from './components/mesh/MeshDeviceSetupModal.vue'
 import ExternalExplorerModal from './components/ExternalExplorerModal.vue'
+import AppConfirmModal from './components/AppConfirmModal.vue'
 import LndSeedBackupPrompt from './components/LndSeedBackupPrompt.vue'
 import LightningRequiredModal from './components/LightningRequiredModal.vue'
 import { useMeshStore } from './stores/mesh'