When clicking on the Add page button, remember the current page

It is necessary to set the current page as a parent in the parent page selection field

Steps to reproduce:
- run docs instance
- auth via /auth
- go to some existing page
- click "Add new page"
- You will see that new page will be created in the "Root", but it would be much more convenient if there was a page that the user was on before

Run the docs instance, authenticate via /auth, open an existing page, and click "Add new page" to reproduce the current Root selection. Trace the Add new page flow and parent page selection, then verify that the page where the action began is selected as the parent for the new page.

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