networking.service has no TimeoutStartSec, and this can cause systemd to delay a login prompt

[dan0delellis]

In proxmox8 (debian 12), networking.service can wait forever for ip link add <dev> type bridge to return. This causes the system to seemingly hang forever at boot with no login prompt and no network connectivity.

networking.service does not need to start successfully; the ExecStart just needs to exit, and then systemd-user-sessions.service can start.
Adding TimeoutStartSec=10s will at least let users log into the system to diagose and rectify the issue.