Collections: Add drag-and-drop row ordering

[priethor]

What

Adds drag-and-drop ordering to collection rows. The saved order works in full-screen collections and embedded data-view blocks, and it survives reloads. If the view is sorted by a field, dragging a row prompts confirmation before clearing the sort and keeping the dropped order.

Why

Some collections need a hand-picked order. This gives users that without making them add a throwaway sort field.

How

• Saving the order in menu_order.
• Seeding a collection’s first manual order from the order the user is looking at.
• Giving new rows the next available order value, so they append.
• Treating manual order as the default row order in REST and client query planning.
• Adding a DataViews row-drag adapter until DataViews has a native row reorder API.

Testing Instructions

1. Open a collection with at least three rows in table view.
2. Sort by a field, drag a row, click “Keep this order,” and confirm the sort clears.
3. Reload the page and confirm the dropped order is still there.
4. Add a new row and confirm it appears at the end.
5. In an embedded data-view block, drag a row while sorted, cancel the confirmation, and confirm the sorted order stays put.

Screen recording

Grabacion.de.pantalla.2026-05-18.a.las.15.10.32.mov