feat: 移植远程公告中心

从 Axolotl 搬 RemoteAnnouncements.vue，顶栏加公告铃铛。远程拉取先禁用，等接口。

packages/ui/src/composables/index.ts

@@ -8,6 +8,7 @@ export * from './format-number'
 export * from './how-ago'
 export * from './i18n'
 export * from './i18n-debug'
+export * from './modal-stack'
 export * from './page-leave-safety'
 export * from './scroll-indicator'
 export type { ArmorPreviewConfig } from './skin-rendering/armor-preview-types'