Color Picker: Styling for drag handle at swatch items

[bjarnef]

Prerequisites

• I have added steps to test this contribution in the description below

Description

As title says it add styling for drag handle and makes it consistent with other parts of backoffice UI.

[github-actions]

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[Copilot]

Pull Request Overview

Adds styling and a CSS class to the drag handle icon in the multiple color picker item input to make its affordance consistent with other backoffice UI elements.

• Adds a handle class to the grip icon.
• Introduces grab/grabbing cursor styles for better visual feedback.

[AndyButland]

Agree this looks better, thanks again @bjarnef.