Standardized GtkCellRendererText foreground bindings to use the palette foreground property macro across user list, notify list, and DCC views (GTK2/GTK3 aware).

Generated GTK3 caret-color CSS using GdkRGBA string conversion instead of manual RGB math for input styling.
Simplified palette RGB16 parsing by building a GdkRGBA-compatible color string before parsing.

src/fe-gtk/userlistgui.c

@@ -547,15 +547,9 @@ userlist_add_columns (GtkTreeView * treeview)
 	if (prefs.hex_gui_compact)
 		g_object_set (G_OBJECT (renderer), "ypad", 0, NULL);
 	gtk_cell_renderer_text_set_fixed_height_from_font (GTK_CELL_RENDERER_TEXT (renderer), 1);
-#if GTK_CHECK_VERSION(3,0,0)
 	gtk_tree_view_insert_column_with_attributes (GTK_TREE_VIEW (treeview),
 																-1, NULL, renderer,
-													"text", 1, "foreground-rgba", 4, NULL);
-#else
-	gtk_tree_view_insert_column_with_attributes (GTK_TREE_VIEW (treeview),
-																-1, NULL, renderer,
-													"text", 1, "foreground-gdk", 4, NULL);
-#endif
+													"text", 1, PALETTE_FOREGROUND_PROPERTY, 4, NULL);
 
 	if (prefs.hex_gui_ulist_show_hosts)
 	{