refactor: introduce modern frontend

frontend/src/main.ts

@@ -0,0 +1,12 @@
+import { createApp } from 'vue'
+import { createPinia } from 'pinia'
+
+import App from './App.vue'
+import router from './router'
+
+const app = createApp(App)
+
+app.use(createPinia())
+app.use(router)
+
+app.mount('#app')