Refine update apps page design

### Problem

First time I saw the update page I thought something is wrong with a layout, or this are the artifacts after resize animation. Turns out it's just the grid design for up-to-date apps conflicts with a row design of an apps that can be updated.


### Proposal

I propose to visually separate the apps the can be updated from the apps that are up to date.
* simple separator line can be used (this will make both areas even)
* color the background of the grid of up-to-date apps or to-be-updated apps (this will make one of the areas stand off)

### Prior Art (Optional)

_No response_