[ui] route all native alert()/confirm() through the site notification system

Every browser alert()/confirm() now uses the app's UI instead of native dialogs
(no prompt() existed). Two new pieces:

- js/ui/confirmDialog.js — showConfirm(message, opts) -> Promise<boolean>, a styled
  `bv-modal modal-always-on-top` dialog (Confirm/Cancel/backdrop/Escape; danger variant
  focuses Cancel). Importable anywhere, so future confirmations use it too. It stacks
  above other modals and is typable thanks to the recent stacked-modal focus fix.
- js/ui/appNotify.js — notifyError/notifyStatus/notifySuccess routing to the app's
  NotificationController, for modules without a local showError; re-exports showConfirm.

Migrated: UploadModal (10 alert -> this.showError, 1 confirm), subscriptionHistory
(3 alert -> notify*, 1 confirm), MyVideosController (2), ProfileStorage/Wallet/Relay
controllers, profileModalController (2), settingsRestorePrompt (default confirm now
showConfirm), nostr/client deleteAllVersions. confirmSyncOverwrite helpers made async
(syncConflict already awaits confirmOverwrite).

Tests: tests/confirm-dialog.test.mjs (6 — confirm/cancel/backdrop/Escape resolution,
DOM cleanup, danger focus, no-DOM fallback). Build + lint clean; affected suites green.
(Note: build/lint don't parse JS — caught a multi-line-import split + a wrong import
path via module-import checks.)

Co-Authored-By: Claude Opus 4.8 <[email protected]>

js/ui/profileModal/ProfileStorageController.js

@@ -10,6 +10,7 @@ import { getActiveSigner } from "../../nostr/client.js";
 import { DEFAULT_NIP07_ENCRYPTION_METHODS } from "../../nostr/nip07Permissions.js";
 import { storageSyncService } from "../../services/storageSyncService.js";
 import { StorageCorsHelp } from "./storageCorsHelp.js";
+import { showConfirm } from "../confirmDialog.js";
 import {
   fillStorageForm,
   clearCredentialFields,
@@ -241,12 +242,10 @@ export class ProfileStorageController {
   }
 
   confirmSyncOverwrite() {
-    if (typeof window === "undefined" || typeof window.confirm !== "function") {
-      return true;
-    }
-    return window.confirm(
+    return showConfirm(
       "A newer copy of your storage settings is on your account (changed on " +
-        "another device). Overwrite it with this one?"
+        "another device). Overwrite it with this one?",
+      { confirmLabel: "Overwrite", danger: true },
     );
   }