Styles: add drag-accept style to icon groups

[danirabbit]

Fixes #532

Drag a running app to a workspace for example

[wpkelso]

@danirabbit I'm not seeing anything different

Kooha-2026-01-23-15-29-00.webm

[danirabbit]

Yeah for whatever reason it looks like it's not giving the drag event in Gala, gonna move to draft

Kooha-2026-01-23-12-35-24.mp4

[leolost2605]

Yes dragging from gala to the dock isn't "real" drag and drop via the protocol but instead via dbus which is handled in the windowdragmanager. I think setting state flags of the current_icon_group in windowdragmanager to drop active everywhere we call window_entered and unsetting it when we call window_left could work.

[flodavid]

I tested this and it appears that icons are blurry when a workspace is hovered. I guess what is happening is that the icons are downscaled for them to fit in the workspace square, but then they are slightly upscaled from the lower resolution when the workspace square is enlarged.
This is not a major issue, but it would be nice if it could be improved.

Example with the cogs where details are all blurred out. 1080p monitor with normal scaling. Dock size increased for the example, but also visible with normal size:

[danirabbit]

The only way to keep perfectly sharp icons would be not to scale them at all, which I suppose we could do but we'd have to rewrite the icon grid to not be a child of the container we're styling with the scale effect. But that would also effect button presses, so it would be fairly complicated

[danirabbit]

@leolost2605 can I get a re-review? I'd love to get this into the next release :)

[danirabbit]

@flodavid can you open a separate issue report about this? It's worth investigating in a follow up branch I think