feat(i18n): 管理端与玩家端三语支持（中/英/马来语）

- 管理后台 adminT 文案库、结算与代理端页面、表单校验
- 玩家端 vue-i18n 补全首页/公告/串关与 ms 文案
- Element Plus ms 语言包与共享 locale 工具

apps/admin/src/composables/useAdminLocale.ts

@@ -0,0 +1,36 @@
+import { ref, computed } from 'vue';
+import {
+  ADMIN_LOCALES,
+  adminT,
+  adminLocaleTag,
+  type AdminLocale,
+} from '../i18n/admin-messages';
+
+const STORAGE_KEY = 'admin_locale';
+
+const locale = ref<AdminLocale>(
+  (localStorage.getItem(STORAGE_KEY) as AdminLocale) || 'zh-CN',
+);
+
+export function getAdminLocale(): AdminLocale {
+  return locale.value;
+}
+
+export function useAdminLocale() {
+  const t = (key: string, params?: Record<string, string | number>) =>
+    adminT(locale.value, key, params);
+
+  function setLocale(code: AdminLocale) {
+    locale.value = code;
+    localStorage.setItem(STORAGE_KEY, code);
+    document.cookie = `${STORAGE_KEY}=${encodeURIComponent(code)};path=/;max-age=31536000;SameSite=Lax`;
+  }
+
+  return {
+    locale: computed(() => locale.value),
+    localeTag: computed(() => adminLocaleTag(locale.value)),
+    locales: ADMIN_LOCALES,
+    setLocale,
+    t,
+  };
+}