Sidebar menu obstructs Add Contact form on medium screen

Related to: https://github.com/nextcloud/server/issues/16934

Describe the bug

On a medium screen, such as a tablet, when clicking the "+ New contact" button, the sidebar remains visible and is not possible to collapse. This makes it impossible to fill in the contact details form, as the sidebar overlaps the form fields.

To Reproduce
Steps to reproduce the behavior:

1. Go to Contacts
2. Click on the hamburger menu to show the sidebar
3. Observe that the sidebar overlaps the form
4. Observe there is no visible way to collapse the sidebar

Expected behavior
The sidebar would automatically collapse when clicking on "+ New contact", revealing the full form contents.

Actual behavior
The sidebar remains open and the hamburger icon disappears, obstructing the form with no way to collapse the sidebar.

Screenshots

Server configuration

Nextcloud version: 20.0

Contacts version: 3.4.1

Reproduce the issue in the Contacts app on a medium-sized screen using the listed steps, with the sidebar open before selecting "+ New contact." Inspect the responsive sidebar and form behavior; done means the sidebar collapses automatically and all contact form fields remain accessible without a visible hamburger control.