Account settings are basically unusable on mobile

[JammingBen]

Initial Checklist

• I understand this is a bug report and questions should be posted in the Community Discussions
• I searched issues and couldn’t find anything (or linked relevant results below)

Bug Description

The account settings are basically unusable on mobile screen sizes because the left nav doesn't transform to a button like e.g. in the files app.

Reproduction Steps

• switch to a mobile resolution
• go to the account settings

Expected Outcome

The left nav transforms into a button and a dropdown menu for screens <640px (just like in the files app).

Actual Outcome

The nav stays, the account settings become unusable.

The implementation of the nav in the account settings should be refactored to use the same desktop- and mobile-nav as other apps (files, admin-settings).