[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/profileModalController.js

@@ -6,6 +6,7 @@ import {
   MAX_WALLET_DEFAULT_ZAP as CONFIG_MAX_WALLET_DEFAULT_ZAP,
   ENABLE_NIP17_RELAY_WARNING as CONFIG_ENABLE_NIP17_RELAY_WARNING,
 } from "../config.js";
+import { showConfirm } from "./confirmDialog.js";
 import { normalizeDesignSystemContext } from "../designSystem.js";
 import { RUNTIME_FLAGS } from "../constants.js";
 import {
@@ -1926,14 +1927,17 @@ export class ProfileModalController {
     }
 
     if (this.profileSubscriptionsBackupBtn) {
-      this.profileSubscriptionsBackupBtn.addEventListener("click", () => {
+      this.profileSubscriptionsBackupBtn.addEventListener("click", async () => {
         const pubkey = this.normalizeHexPubkey(this.getActivePubkey());
-        if (pubkey) {
-          if (confirm("Create a backup of your current subscription list?")) {
+        if (
+          pubkey &&
+          (await showConfirm("Create a backup of your current subscription list?", {
+            confirmLabel: "Create backup",
+          }))
+        ) {
              this.subscriptionHistoryController.handleCreateBackup(pubkey).then(() => {
                  this.showSuccess("Backup created.");
              });
-          }
         } else {
           this.showError("Please log in to backup subscriptions.");
         }
@@ -2930,7 +2934,7 @@ export class ProfileModalController {
             ? confirmValue.trim()
             : "this entry";
         const prompt = confirmMessage.replace("{npub}", replacement);
-        if (!window.confirm(prompt)) {
+        if (!(await showConfirm(prompt, { danger: true }))) {
           return;
         }
       }