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/tailwind.config.js

@@ -3,6 +3,7 @@ export default {
     "./index.html",
     "./src/**/*.{vue,js,ts,jsx,tsx}",
   ],
+  darkMode: 'class',
   theme: {
     extend: {
       backdropBlur: {