Unify config into shell.json and add Noctalia plugin support

default/quickshell/omarchy-shell/Commons/ThemeIcons.qml

@@ -0,0 +1,10 @@
+pragma Singleton
+import QtQuick
+
+// Noctalia compat shim. Their plugins resolve app icons through XDG icon
+// themes; we don't ship that machinery, so iconForAppId returns empty and
+// callers fall back to their default glyph.
+QtObject {
+  function iconFromName(name) { return "" }
+  function iconForAppId(appId) { return "" }
+}