fix(logout)!: clear Inertia prefetch cache on logout to prevent data leakage

[SkandarS0]

Issue

This PR fixes a potential security issue where cached data is not cleared on user logout, leading to possible data leakage in multi-user environments.

Steps to Reproduce

These steps should be done within less 30 seconds as the cache duration for the Settings link button is set to the default duration.

Open your browser's DevTools to track prefetching requests.

1. Log in as User A.
2. Hover over the Settings link button when data will be prefetched.
3. Log out and log in as User B.
4. Upon hovering over the Settings link button, no data will be prefetched as there is already cached data about User A.
5. Clicking the Settings link button will result in showing the profile's settings BUT with User A's data.

Video demonstration

Screen.Recording.2025-04-09.181727.mp4

Solution

Added a call to router.flushAll() in the logout process to clear the Inertia prefetch cache.

Video demonstration

Screen.Recording.2025-04-09.182602.mp4

[tnylea]

Hey @SkandarS0, thanks for the thorough explanation and the videos. Really appreciate it. I've added this same fix to the Vue Starter Kit here: laravel/vue-starter-kit#116.

Vue version did not use the prefetch attribute, so it was not an issue, but to keep things consistent, I've added the attribute and the flush method.

Appreciate it!