fix: avoid clearing saved redirect in onBeforeMount to prevent race with submit

When Login.vue re-mounts inside the authenticated layout after a
successful login, its onBeforeMount hook fires again. If it calls
redirectIfSaved(), it clears the saved route from localStorage before
the submit() handler's redirectIfSaved() can use it, causing a redirect
to home instead of the saved route. Use router.push({name: 'home'})
directly since the only purpose here is to redirect already-authenticated
users away from the login page.

frontend/src/views/user/Login.vue

@@ -125,6 +125,7 @@
 <script setup lang="ts">
 import {computed, onBeforeMount, ref} from 'vue'
 import {useI18n} from 'vue-i18n'
+import {useRouter} from 'vue-router'
 import {useDebounceFn} from '@vueuse/core'
 
 import Message from '@/components/misc/Message.vue'
@@ -143,6 +144,7 @@ import {useTitle} from '@/composables/useTitle'
 const {t} = useI18n({useScope: 'global'})
 useTitle(() => t('user.auth.login'))
 
+const router = useRouter()
 const authStore = useAuthStore()
 const configStore = useConfigStore()
 const {redirectIfSaved} = useRedirectToLastVisited()
@@ -171,9 +173,13 @@ onBeforeMount(() => {
 		errorMessage.value = e.message
 	})
 
-	// Check if the user is already logged in, if so, redirect them to the homepage
+	// Check if the user is already logged in, if so, redirect them to the homepage.
+	// We intentionally use router.push here instead of redirectIfSaved() because
+	// this hook also fires when Login.vue re-mounts inside the authenticated layout
+	// after a successful login. Using redirectIfSaved() here would clear the saved
+	// route before the submit() handler gets a chance to use it.
 	if (authenticated.value) {
-		redirectIfSaved()
+		router.push({name: 'home'})
 	}
 })