Remember Me causes ghost login after concurrent login

[belcirelk]

[x]: This is a bug and not a question.

[x]: I understand that the best way to resolve this issue is to solve it and propose a Pull Request.

Describe the bug**

When a user logs in with “Remember Me” enabled from multiple browsers or devices, LibreBooking can enter an inconsistent authentication state. The user appears logged in after a page reload, but the PHP session is invalid, leading to missing user data and errors when performing actions such as reservations.

To Reproduce**

Steps to reproduce the behavior:

1. Login Browser A with remember me
2. Login Browser B with remember me
3. Return to Browser A. Close it and return to login page.
4. Reload twice (first time you have login page, second time the dashboard with a broken logged-in state (see the profile page).

Expected behavior**

The dashboard should not be displayed.

Screenshots**

Additional context**

Specifications

• LibreBooking version (or SHA if using the develop branch):