UI reacts on SSEs for added/removed favorite-items

[schweigisito]

Initial Checklist

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

Idea

Currently UI doesn't react on SSEs sent by backend once itmes get put to or removed from favourites. To be consistent with other file item events, would be nice to also react to favourite related events.

This also requires backend to actually send events.