Updated GTK3 icon rendering paths in affected UI helpers to call gtkutil_image_new_from_stock(...), which is the path that resolves zc-menu-* resources correctly and consistently from data/icons/menu (instead of raw theme lookup).
Added new icons to the shared bundled menu icon set (light/dark) for copy, delete, add, remove, spell-check, and refresh, and registered them in the GResource manifest so they are always available at runtime.