Change ImageViewer code structure and fix cursor behavior

[skidoodle]

Description

This PR refactors the ImageViewer component to clean up the code and improve the user experience during drag interactions.

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings

[skidoodle]

I have accidentally commited #2656 too, I have reverted it, but note that it needs #2656 to work properly.