Missing page container in branching visualization for "End page"

## Description

In Branching View, End page does not have a container / expected styling similar to other pages

## Screenshots

Start by running the platform-forms-client application and opening Branching View, then compare the End page with the other page containers shown in the issue screenshots. Trace the Branching View entry point and its page rendering to find where the End page styling diverges; done means it has the expected container and styling consistently with the other pages.

Written by the indexing model from the issue text.