feat: Enhance logout functionality and routing in authentication system

- Integrate `useRouter` in `UserProfile.vue` and `useAuth.ts` to manage navigation after logout.
- Update `handleLogout` in `Navbar.vue` to reflect that redirection is now handled within the `auth.logout()` function.

src/components/auth/UserProfile.vue

@@ -1,5 +1,6 @@
 <script setup lang="ts">
 import { computed } from 'vue'
+import { useRouter } from 'vue-router'
 import { Button } from '@/components/ui/button'
 import { Card, CardContent, CardDescription, CardHeader, CardTitle } from '@/components/ui/card'
 import { Badge } from '@/components/ui/badge'
@@ -7,6 +8,7 @@ import { User, LogOut, Settings } from 'lucide-vue-next'
 import { auth } from '@/composables/useAuth'
 import { toast } from 'vue-sonner'
 
+const router = useRouter()
 const userDisplay = computed(() => auth.userDisplay.value)
 
 async function handleLogout() {