feat(auth) : redirect client users to /portal after login and extract ticket helpers composable

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

frontend/pages/login.vue

@@ -63,7 +63,8 @@ const handleSubmit = async () => {
     try {
         await auth.login(username.value, password.value)
 
-        await router.push('/')
+        const isClient = auth.user?.roles?.includes('ROLE_CLIENT') ?? false
+        await router.push(isClient ? '/portal' : '/')
     } finally {
         isSubmitting.value = false
     }