Battery Icon Design & Charging Indicator Visibility Improvement on Bar

### Feature Description

The current battery icon design is not very clear or visually appealing. The battery icon is vertical, but a horizontal battery style would look much cleaner and more modern in the panel.

Also, the charging indicator/icon on the battery is extremely small. When the laptop is charging, there is almost no visible difference between charging and non-charging states. Literally, you have to look very carefully to notice it.

### with charging

### without charging

### Use Case

Battery status is something users constantly look at throughout the day. Right now, it is difficult to quickly identify whether the laptop is charging or not because the charging icon is too small and unclear.

A cleaner horizontal design with a more visible charging indicator would improve usability and accessibility.

Why is this feature important?
Better visibility
Easier to identify charging state instantly
More modern and polished UI appearance
Improved user experience, especially on smaller screens or high-resolution displays

### Compositor(s)

Niri

### If Other, please specify

_No response_

### Proposed Solution

Use a horizontal battery icon similar to modern desktop/mobile UIs and redesign the charging overlay/icon so it is clearly visible at a glance.

The charging state could also include:

a bold lightning icon
animated charging effect
different accent color while charging

### Alternatives/Existing Solutions

Many desktop environments and mobile operating systems use horizontal battery icons with clear charging indicators, including:

Android
GNOME extensions/widgets
Material Design battery icons
KDE Plasma battery indicators

No source file, test, or entry point is named. Start by locating the bar's battery icon and its charging-state rendering, then compare both states at the size shown in the issue. Done means a horizontal icon and a charging indicator that are clearly distinguishable at a glance.

Written by the indexing model from the issue text.