Centralized the palette foreground property definition for GTK2/GTK3 and applied it to the user list, notify list, and DCC tree renderers to use RGBA where supported.

Removed legacy colormap allocation/free calls in palette handling and setup color selection while preserving the GTK2 path logic.

src/fe-gtk/userlistgui.c

@@ -528,11 +528,7 @@ userlist_add_columns (GtkTreeView * treeview)
 	gtk_cell_renderer_text_set_fixed_height_from_font (GTK_CELL_RENDERER_TEXT (renderer), 1);
 	gtk_tree_view_insert_column_with_attributes (GTK_TREE_VIEW (treeview),
 																-1, NULL, renderer,
-#if GTK_CHECK_VERSION(3,0,0)
-													"text", 1, "foreground-rgba", 4, NULL);
-#else
-													"text", 1, "foreground-gdk", 4, NULL);
-#endif
+													"text", 1, PALETTE_FOREGROUND_PROPERTY, 4, NULL);
 
 	if (prefs.hex_gui_ulist_show_hosts)
 	{