feat(transfer): implement drag-n-drop functionality for transfer

[arina-gutuboe]

Implements LIBS-764

---

Description

Implements drag-and-drop functionality for the Transfer component, built on top of @dnd-kit/core.

Options can now be dragged between the source and picked lists with a pointer, in addition to the existing action buttons and double-click.
When enableOrderChange is set, the picked list can also be reordered by dragging, and options dropped onto it are inserted at the drop position; without that flag, dropped options are appended to the end.
Dragging a highlighted option drags the whole highlighted set.

Changes include:

• A new useTransferDnd hook and a set of pure helper functions (resolveDropTarget, resolvePositionalIndex, getDraggedValues, addSourceOptionsOnDrop, reorderPickedOptionsOnDrop), with unit tests.
• New DraggableOption and TransferDragOverlay components (drag overlay with fly-back/fade drop animation for cancelled or no-op drops).
• Updates the transfer-related features to integrate the DnD logic with existing highlighting/filtering behavior.
• Updated documentation and added new Storybook demos: Drag and drop, Drag and drop without reordering, Drag and drop with disabled options.

---

Checklist

• API docs are generated
• Tests were added
• Storybook demos were added

---

Video

https://dhis2.atlassian.net/browse/UX-183?focusedCommentId=249751

[dhis2-bot]

🚀 Deployed on https://pr-1758--dhis2-ui.netlify.app

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud