Updates ROS2 version (with heartbeat and node monitor)

[Cyano0]

What type of PR is this? (check all applicable)

• Refactor
• Feature
• Bug Fix
• Optimization
• Documentation Update

Description

This PR adds dual-level heartbeat monitoring in Sentor:

1. Safety heartbeat (safety/heartbeat) – driven by safety_critical checks
2. Warning heartbeat (warning/heartbeat) – driven by autonomy_critical checks

Other key pieces added:

• NodeMonitor class to track ROS 2 node liveness.
• Updated TopicMonitor and SafetyMonitor to expose both is_alive and is_autonomy_alive.
• New YAML flags (autonomy_critical) + extended README with detailed config guidance.
• Example config (test_monitor_config.yaml) covering topic + node monitors.

Related Tickets & Documents

• Related Issue #
• Closes #

QA Instructions, Screenshots, Recordings

Please replace this line with instructions on how to test your changes.

[optional] Are there any post deployment tasks we need to perform?

[marc-hanheide]

replaced by #60