Allow for setting different margin for sides and top/bottom for Bar

## Feature Description

Being able to specify different margins for the sides and top/bottom for the bar.

## Use Case

It allows me, for example, to reduce the bar width without pushing it down (because when increasing the edge spacing, it increases in all directions)

## Compositor

Is this feature specific to one compositor?

- [ ] All compositors
- [ ] niri
- [x] Hyprland
- [ ] dwl (MangoWC)
- [ ] sway

## Proposed Solution

Separate the slider into two, sides and top/bottom

For example hyprpanel allows this

I belive this can be done with `gtk_layer_set_margin` so maybe something similar exists for quickshell

(quick search for PanelWindow)

## Alternatives/Existing Solutions

Start by locating PanelWindow in the Quickshell code and comparing its margin handling with gtk_layer_set_margin. Confirm how the Hyprland bar currently applies edge spacing, then separate side and top/bottom controls so the bar width can change without changing its vertical position.

Written by the indexing model from the issue text.