Issue #4: Implement Constant temperature function in GUI. This is useful to verify the oven parameters

stm-firmware/ui/menu.c

@@ -81,6 +81,8 @@ void menu_entry_dropback(struct lcd_menu *menu, menu_func_t parent_func)
 	else
 		menu->active_entry = menu->root_entry;
 
+	menu_ack_rotary_delta(menu);
+
 	menu->active_entry_type = MENU_ENTRY_DROPBACK;
 }