Handle polkit timeout during udev setup

[Ajeem-git]

Summary: Prevent a crash when the authentication dialog times out while saving udev scheduling rules.

What changed:

• Convert org.freedesktop.DBus.Error.NoReply from SetupUdev.save() into an internal Timeout condition.
• Catch Timeout in Config._setup_event_based_automation(), notify the user, and return without crashing.

Why:
When the polkit password prompt times out, the D-Bus call returns NoReply. That exception was not handled in the udev setup path, so the Manage Profiles dialog crashed instead of reporting the failure gracefully.

Verification:

• Traced the exception path from the issue traceback.
• Verified the updated files compile with python3.11 -m py_compile common/tools.py common/config.py.

Note:
I could not fully reproduce the Linux polkit dialog flow on macOS, so this is a traceback-driven fix.

[buhtz]

Hello Ajeem,

thank you for your contribution and taking time to improve Back In Time. I appreciate it.

On a quick initial review your PR looks good. I'll review it in detail later.

Please note that currently I have to put all PRs on hold, because the Back In Time code base is in a transition phase. I am rewriting the mounting subsystem from scratch (PR #2449). Since the components are not well isolated, this affects nearly every file. To avoid complex merge conflicts, all other PRs are temporarily on hold.

Best wishes,
Christian