Replace bar-settings with unified settings plugin

Consolidates bar-settings into a single 'settings' plugin with sidebar
categories: Defaults, Style, Bar, System, Plugins. Updates supporting
commands (omarchy-launch-settings, omarchy-style-corners-quickshell,
omarchy-theme-list-with-previews, omarchy-hyprland-monitor-scaling-set)
and refreshes sidebar glyphs to Nerd Font icons.

bin/omarchy-shell-ipc

@@ -11,7 +11,7 @@ Starts omarchy-shell if not running, then forwards a quickshell ipc call.
 
 Examples:
   omarchy-shell-ipc shell ping
-  omarchy-shell-ipc shell summon omarchy.bar-settings "{}"
+  omarchy-shell-ipc shell summon omarchy.settings "{}"
   omarchy-shell-ipc shell hide omarchy.image-picker
   omarchy-shell-ipc shell listPlugins
   omarchy-shell-ipc shell listShellConfig