feat(app): add WGRplane web UI and backend features

- Add Vue 3 frontend with glassmorphism design (Tailwind CSS)
- Add Go backend handlers: auth, webhooks, stats, scheduler, validation
- Add i18n support (EN, ID, ZH)
- Add Swagger docs and API handlers
- Add nftables integration and plugins support
- Remove deprecated go.mod (migrated to wgrplane)

app/frontend/src/i18n/index.ts

@@ -0,0 +1,15 @@
+import { createI18n } from 'vue-i18n'
+import en from './locales/en.json'
+import id from './locales/id.json'
+import zh from './locales/zh.json'
+
+export const i18n = createI18n({
+  legacy: false,
+  locale: 'en',
+  fallbackLocale: 'en',
+  messages: {
+    en,
+    id,
+    zh
+  }
+})