Block Grid: Styling of group drag with handle

[bjarnef]

Prerequisites

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

Description

Added a drag handle to be consistent with other parts of backoffice UI and indicate groups are draggable.

I made it a bit more consistent with configuration of other datatypes and navigating via keyboard is not possible to see when delete button has focus.

It we want to use auto-width of group input, I think it at least should have a minimum width.

chrome_Gpz0Cggrxq.mp4

[github-actions]

Hi there @bjarnef, thank you for this contribution! 👍

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[Copilot]

Pull Request Overview

This PR improves the visual styling of the block grid group drag functionality by adding proper drag handles and cursor states.

• Adds a grip icon to visually indicate draggable groups
• Implements proper flexbox layout for the group handle
• Adds active cursor state for better user feedback during drag operations

[AndyButland]

Looks and works nicely, thanks @bjarnef.