fix(app-headless-cms): wire dropConfirmation to FolderTree and block visual update until confirmed

[Pavel910]

Summary

• Wire the dropConfirmation config prop from ContentEntryListConfig through to FolderTree in the HeadlessCMS sidebar — it was resolved but never passed
• Fix the Tree component (admin-ui) to run onDrop before the visual tree update, so consumers can block or cancel the reorder
• Wrap the folder move confirmation dialog in a promise so onDrop blocks until the user confirms or cancels, preventing the premature visual move
• Add a test extension (extensions/folderDropConfirmation) demonstrating Browser.Folder.DropConfirmation

Changes

• packages/app-headless-cms/.../SidebarContent.tsx — pass dropConfirmation prop to FolderTree
• packages/admin-ui/src/Tree/useTree.ts — move presenter.handleDrop after onDrop; catch throws to skip the visual update on cancellation
• packages/app-aco/.../List.tsx — wrap confirmation dialog in a blocking promise
• packages/app-aco/.../useConfirmMoveFolderDialog.tsx — forward onClose callback to the dialog system
• extensions/folderDropConfirmation/index.tsx + webiny.config.tsx — test extension registration

Test plan

• Enable the test extension, drag a folder in CMS content entry list
• Confirm dialog appears and folder does NOT move until "Move folder" is clicked
• Clicking "Cancel" leaves the folder in its original position
• Without the extension (dropConfirmation=false), folders drag-and-drop without a dialog as before
• Website Builder navigator drag-and-drop still works (other Tree consumer)