feat(desktop): embed BoosAPI Desktop client as a subproject

Vendor the rebranded BoosAPI Desktop client (Tauri + Vue) into metapi as
a monorepo subdirectory under desktop/. Source only — node_modules,
dist, Cargo target and the upstream .git history are excluded.

desktop/ keeps its own independent Cargo workspace (desktop/src-tauri
with crates/*); it is not part of the backend boosapi crate, so a
`cargo check` at the metapi root still compiles only the backend. Build
the desktop app from desktop/src-tauri per desktop/README.md.

Note: app icons are still placeholder assets pending the final BoosAPI
logo. The updater signing keys live outside the repo and are not
included.

desktop/src/i18n/index.ts

@@ -0,0 +1,36 @@
+import i18n from 'i18next';
+import { initReactI18next } from 'react-i18next';
+import zhCN from './locales/zh-CN.json';
+import zhTW from './locales/zh-TW.json';
+import enUS from './locales/en-US.json';
+import ja from './locales/ja.json';
+import ko from './locales/ko.json';
+import fr from './locales/fr.json';
+import de from './locales/de.json';
+import es from './locales/es.json';
+import ru from './locales/ru.json';
+import hi from './locales/hi.json';
+import ar from './locales/ar.json';
+
+i18n
+  .use(initReactI18next)
+  .init({
+    resources: {
+      'zh-CN': { translation: zhCN },
+      'zh-TW': { translation: zhTW },
+      'en-US': { translation: enUS },
+      ja: { translation: ja },
+      ko: { translation: ko },
+      fr: { translation: fr },
+      de: { translation: de },
+      es: { translation: es },
+      ru: { translation: ru },
+      hi: { translation: hi },
+      ar: { translation: ar },
+    },
+    lng: 'zh-CN',
+    fallbackLng: 'zh-CN',
+    interpolation: { escapeValue: false },
+  });
+
+export default i18n;