[DEFECT] Rollback UVE container add-item buttons from click-to-reveal back to hover-to-reveal

Problem Statement

In a recent change, the UVE (Universal Visual Editor) container interaction was modified so that the add-item buttons (+) inside containers are only revealed when the user clicks on the container. Previously, those buttons were revealed on hover.

This change has caused recurring confusion across multiple customers, who are reporting it as a bug:

• Users do not realize they need to click on the container before they can add content.
• When a container is empty, it has no visible outline/handle, so users do not see anything to click on at all.
• Support has received several tickets about this behavior, even though technically it is "working as designed" after the change.

The hover-based interaction was discoverable; the new click-based interaction is not. We need to roll back the change and restore the original hover-to-reveal behavior for the add-item buttons inside containers in UVE.

Browser/OS: All (UVE editor, frontend regression).

Steps to Reproduce

1. Open the UVE (Universal Visual Editor) on any page that contains containers.
2. Hover the mouse over a container (especially an empty one).
3. Observe that the + (add item) buttons are not shown until the container is clicked.

Expected: Hovering over a container reveals the + add-item buttons (previous behavior).
Actual: The container must be clicked first before the + buttons become visible. Empty containers have no visible affordance at all, so users cannot find where to click.

Acceptance Criteria

• Hovering the mouse over any container in UVE reveals the + add-item buttons immediately, without requiring a prior click.
• The hover-reveal behavior works the same for empty containers and for containers with existing content.
• The previous click-to-reveal behavior is removed (full rollback) so that the interaction matches the pre-change UX.
• Behavior is verified across the supported browsers (Chrome, Firefox, Safari, Edge).
• Existing add-content flow continues to work end-to-end after the rollback (clicking + still opens the add-item dialog as before).
• No regression in container selection, drag-and-drop, or other UVE interactions.

dotCMS Version

Latest from main branch (regression introduced after the hover-to-click change in UVE container interaction). To be confirmed during triage with the exact release version.

Severity

Medium - Some functionality impacted

Links

• https://helpdesk.dotcms.com/a/tickets/36945

Start by locating the UVE container interaction code that changed add-item buttons from hover-to-reveal to click-to-reveal, then inspect the related interaction tests if present. Restore hover visibility for both empty and populated containers, and verify the add-item dialog, selection, drag-and-drop, and supported-browser behavior against the acceptance criteria.