Sidebar strikethrough reset fix

[bartbutenaers]

Description

Steps to reproduce:

1. Hide a group in the sidebar (via the eye button), then the text will automatically become strikethrough:

   

2. Edit that group (via the edit button), and press the "Done" button of the ui-page config screen.

3. The sidebar tree will automatically refresh, but the value of the visible attribute has become a string "false" (instead of a boolean false):

   

4. Because the CSS class "nr-db2-sb-item-hidden" is not applied anymore, the strikethrough will be gone (although the group is still not visible).

I have fixed this by supporting string "false" similiar to how it is done for the eye-icon, because that icon is showing the correct status. And we need to keep the eye-icon status and the strikethrough of the label in sync:

Note that the real root cause is in the ui-page hml config screen, which converts the visible property value from a boolean to a string, but that is already reported in another issue (and I will fix that in another PR).

Related Issue(s)

1296

Checklist

• I have read the contribution guidelines
• Suitable unit/system level tests have been added and they pass
• Documentation has been updated
  • Upgrade instructions
  • Configuration details
  • Concepts
• Changes flowforge.yml?
  • Issue/PR raised on FlowFuse/helm to update ConfigMap Template
  • Issue/PR raised on FlowFuse/CloudProject to update values for Staging/Production

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