feat(#9): Nuxt 4 migration

legalconsenthub/app/pages/callback.vue

@@ -0,0 +1,19 @@
+<template>
+  <h1>Authentication callback processing...</h1>
+</template>
+
+<script setup lang="ts">
+import { useKeycloak } from '~/composables/useKeycloak'
+
+const { userManager } = useKeycloak()
+
+onMounted(async () => {
+  try {
+    const user = await userManager.signinRedirectCallback()
+    console.log('User logged in', user)
+    await navigateTo('/')
+  } catch (e) {
+    console.error('Error during login', e)
+  }
+})
+</script>