Log out an idle user after short timeout

**Is your feature request related to a problem? Please describe.**
If the user keeps working on a project and do not log out, it may block the other users.

**Describe the solution you'd like**
Logout the user automatically after a certain time period (15 minutes)

**Describe alternatives you've considered**
N/A

**Additional context**
This may be related to https://github.com/asyml/stave/issues/102

The issue names no files, tests, or entry points. First locate the existing session and logout handling, then determine how idle time is tracked and where a 15-minute timeout belongs. Done means an idle user is logged out after 15 minutes while active work is not interrupted, with coverage for both behaviors.

Written by the indexing model from the issue text.