fix(logbook): resolve duplicated comments in add-content and logbook item components

[derangulacau]

Problem

Duplicate comments were being created when adding content via the logbook widget.

Observed behavior

• First logbook: comment appears once
• Subsequent logbooks: same comment appears multiple times

Root Cause

• Multiple active RxJS subscriptions were not cleaned up
• Each widget instance created additional subscriptions
• submitContent() was triggered multiple times

Solution

• Unsubscribed existing changeStream subscriptions before creating new ones
• Cleaned up previous dataService message subscriptions
• Restricted submission logic to the main widget (configIndex === 1)

Result

• Only one active subscription handles events
• Duplicate comment submissions are prevented