feat(taskbar): add configurable active indicator color

[spasche]

Summary

Add a configurable active_indicator_color setting to the taskbar widget.

The selected palette role or fixed hex color is applied to both active-indicator layouts:

• the dot below an icon-only task
• the line below a task that displays its window title

This brings the active-window indicator in line with the taskbar's workspace labels, whose focused, occupied, empty, and urgent colors are already configurable.

The setting defaults to primary to preserve the existing appearance and is only shown in the settings UI when the active-window indicator is enabled.

Motivation

The taskbar's active-window indicator was hard-coded to the primary palette color. This prevented users from styling it independently from other primary-colored UI elements.

Type of Change

• Bug fix
• New feature
• Breaking change
• Refactoring
• Build / packaging

Related Issue

N/A

Testing

• just test
• Manually tested the taskbar with multiple active_indicator_color settings, including palette roles and a fixed hex color.
• Verified the configured color is applied when window titles are disabled and the active indicator is rendered as a dot.
• Verified the configured color is applied when window titles are enabled and the active indicator is rendered as a line.
• Verified toggling the active-window indicator and changing its color through the settings UI.

Manual Coverage

• Tested on Niri
• Tested on Hyprland
• Tested on Sway
• Tested on another compositor:
• Tested with different bar positions and density settings
• Tested at different interface scaling values
• Tested with multiple monitors

Screenshots / Videos

before:

after:

Checklist

• This PR is ready for review, or it is marked as Draft.
• I read and followed the relevant guidance in CONTRIBUTING.md.
• I ran just format with clang-format v22+ installed, or this PR has no code changes.
• I ran the relevant build or test commands, or explained why they were not run.
• I self-reviewed the changes.
• I checked for new warnings or errors.
• I will update end-user documentation after merge, or this PR does not change user-facing configuration or behavior.
• I added or updated assets/translations/en.json, or this PR adds no new user-facing strings.
• I did not edit non-English translation files unless this PR is explicitly for translation tooling, an import/export sync, or a maintainer-requested locale change.
• I used the existing canonical names for config keys, IPC names, paths, and identifiers.

Additional Notes

[ItsLemmy]

Thanks!