Implement fetching apps from BE

Closes #82 (closed) #77 (closed)

To do:

1. Load apps dynamically
   • on Dashboard
   • on (new) Apps tab
2. Show "Monitoring" app the old way, under "Utilities"
3. fix monitoring icon on apps overview and rights overview
4. Only show apps on Dashboard if the user has access rights to them #83 (closed)
5. Show App Status on apps tab (not on Dashboard for now)
   • Do we want this? The easiest way to implement this currently makes the /apps endpoint slower. Another way to implement it is by adding an extra apps/<slug>/status endpoint to the back-end, but I would do that in a separate issue.
6. Make this work with external apps
7. Remove everything from feat/apps-development that we don't need yet