reuse register toast id

frontend/lib/api/auth/register.ts

@@ -1,6 +1,8 @@
 import { toast } from 'vue-sonner';
 import type { ApiResponse } from '#shared/types/api';
 
+const REGISTER_TOAST_ID = 'REGISTER_USER_TOAST' as const;
+
 export async function registerUser(
     username: string,
     email: string,
@@ -24,6 +26,7 @@ export async function registerUser(
 
     if (data.value == null) {
         toast.error('Register', {
+            id: REGISTER_TOAST_ID,
             description: error.value?.data ?? 'Failed to register',
         });
 
@@ -33,6 +36,7 @@ export async function registerUser(
     }
 
     toast.success('Register', {
+        id: REGISTER_TOAST_ID,
         description: `Successfully registered user ${username}`,
     });