[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/services/settingsRestorePrompt.js

@@ -6,6 +6,7 @@
 // if the user accepts.
 
 import { storageSyncService as defaultStorageSync } from "./storageSyncService.js";
+import { showConfirm } from "../ui/confirmDialog.js";
 
 const OFFERED_KEY = "bitvid:settings-sync:offered:v1";
 
@@ -63,10 +64,7 @@ const ITEM_LABELS = {
 export function createSettingsRestorePrompt({
   storageSync = defaultStorageSync,
   walletSync = null,
-  confirm = (message) =>
-    typeof window !== "undefined" && typeof window.confirm === "function"
-      ? window.confirm(message)
-      : false,
+  confirm = (message) => showConfirm(message, { confirmLabel: "Restore" }),
   logger = null,
 } = {}) {
   // Items not already enabled / not already offered on THIS device that have a
@@ -117,7 +115,7 @@ export function createSettingsRestorePrompt({
     }
 
     const list = candidates.map((kind) => ITEM_LABELS[kind]).join(" and ");
-    const accepted = confirm(
+    const accepted = await confirm(
       `Found an encrypted copy of your ${list} on your Nostr account. ` +
         `Restore ${candidates.length > 1 ? "them" : "it"} to this device?`
     );