Feat/toggle auto tracking

[andreacalm]

Summary

Implements automatic tracking control with fallback endpoints:

• VAPIX operator.cgi as the primary option
• Local ACAP settings.fcgi endpoint as a fallback
• Adds periodic synchronization of the automatic tracking status to reflect external changes (web interface/VMS)
• Suppresses manual PTZ commands when auto-tracking is active to prevent interference
• Improves error messages when the model/application does not support auto-tracking
• Updates the README documentation with behavior, fallback, and status synchronization

Validation performed:

• The set_autotracking service is enabled/disabled correctly
• The autotracking_active topic is updated by the service and by detected external changes
• With automatic tracking active, manual PTZ commands are blocked

How to test:

Topic

rostopic echo /axis_camera_ptz/autotracking_active

Enable auto-tracking

rosservice call /axis_camera_ptz/set_autotracking "enable: true"

Disable auto-tracking

rosservice call /axis_camera_ptz/set_autotracking "enable: false"

Note: The VAPIX operator.cgi endpoint has not been validated, as I do not have a compatible camera model. Tests conducted to date have been performed using a single camera, on which automatic tracking was successfully controlled via the local ACAP endpoint.