Before:
(similar to #4181: I do not like the layout at all. The layout is broken on small and big screens)

After:
the box layout, that is used on different other places (f.e. subscription management and user queries)

New:
manage the feed and stay (!) on the idle page (before: redirecting to the subscription management page)

How to test the feature manually:

1. go to subscription management
2. go to "idle feeds" page in the statics section
3. manage some feeds

Pull request checklist:

• clear commit messages
• code manually tested