[web] mobile: Make left sidebar nav available

[exalate-issue-sync]

Description

User Stories

• As a user I need to be able to navigate to every location regardless of my device so that I can work from every device.

Value

Acceptance Criteria

• The following applies only to small screens < 640 breakpoint:
• If the current location is the root of a left sidebar item (like Personal, Shares, Spaces etc.), then show a drop menu with the left sidebar items (see screenshot)
• If the current location is a child folder, show the name of the current folder and a caret-left icon to navigate up (see screenshot)
• If the current location is the root of "Shares", then show the left-sidebar-drop on top of the shared with me/others/via link drop menu (not ideal but good enough for now. suggestions for improvement welcome)
• same pattern for admin-settings app with left sidebar items General, Users, Groups and Spaces (there are no child folders, so all views only show the dropdown with the left sidebar nav items)

Definition of ready

[ ] everybody needs to understand the value written in the user story
[ ] acceptance criteria has to be defined
[ ] all dependencies of the user story need to be identified
[ ] feature should be seen from an end user perspective
[ ] user story has to be estimated
[ ] story points need to be less then 20

Definition of done

• Functional requirements
  [ ] functionality described in the user story works
  [ ] acceptance criteria are fulfilled
• Quality
  [ ] code review happened
  [ ] CI is green
  [ ] critical code received unit tests by the developer
  [ ] automated tests passed (if automated tests are not available, this test needs to be created and passed
• Non-functional requirements
  [ ] no sonar cloud issues