feat(theming): add Equicord paths to system24 theme generation

[yukazakiri]

Summary

Extend the System24 theme generator output path resolution to include Equicord theme directories.

This keeps Equicord support in the same Vesktop generation pipeline (system24_palette.sh -> system24_palette.py) instead of adding client-specific logic to apply-gtk-theme.sh.

Motivation

Vesktop theming is generated centrally by system24_palette.py, which previously targeted only ~/.config/vesktop/themes and ~/.config/Vesktop/themes.

Equicord users need the same generated theme files in Equicord theme directories so wallpaper-driven theme updates apply automatically.

Testing

Steps to verify this works:

1. Run syntax checks:
   • python3 -m py_compile scripts/colors/system24_palette.py
   • bash -n scripts/colors/apply-gtk-theme.sh
2. Run generator with a temp HOME containing ~/.config/equicord/themes and a sample palette.json.
3. Confirm generated files exist in Equicord path:
   • ~/.config/equicord/themes/system24.theme.css
   • ~/.config/equicord/themes/ii-midnight.theme.css

Checklist

• Tested on Niri (or Hyprland if applicable)
• Tested both ii and waffle families for UI changes
• Tested material, aurora, and inir styles for ii changes
• No hardcoded values (colors, fonts, durations use design tokens)
• Config changes synced in Config.qml and defaults/config.json
• Config access uses optional chaining: Config.options?.section?.option ?? default
• IPC functions have explicit return types (: void, : string, etc.)
• Shell restarted after changes: inir restart
• Logs checked for errors: inir logs
• Lazy-loaded components tested (Settings, overlays)
• No console errors or warnings

Related

Closes #
Fixes #