Remove GNOME dependencies and make more desktop-neutral - cleaned

- Remove gsettings-desktop-schemas dependency (GNOME-specific)
- Replace gnome.post_install() with manual gtk4-update-icon-cache
- Remove GNOME import from meson.build
- Make autostart desktop file desktop-neutral (remove GSettings condition)
- Add accessibility categories and keywords to desktop file

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

meson.build

@@ -4,7 +4,6 @@ project('cthulhu',
 )
 
 python = import('python')
-gnome = import('gnome')
 i18n = import('i18n')
 
 python_minimum_version = '3.3'
@@ -105,9 +104,9 @@ i18n.merge_file(
   install_dir: get_option('sysconfdir') / 'xdg' / 'autostart',
 )
 
-gnome.post_install(
-  gtk_update_icon_cache: true,
-)
+# Update icon cache manually (desktop-neutral)
+meson.add_install_script('gtk4-update-icon-cache', '-q', '-t', '-f', 
+                        get_option('datadir') / 'icons' / 'hicolor')
 
 summary += {'Install dir': python.find_installation('python3').get_install_dir()}