12V pcb capacitor for a 2,5V motor lock

We have a lock with a motor and a position switcher. The motor runs with 2,5V and takes 100 to max. 500 mA. The motor should drive to the open position (0,3 seconds) when this unit gets 12V If the tension is 0V again, the capacitor should give the power to the motor. The attached scheme with the realais should work. I also add a scheme of the 12V to 2,5V pcb we already have. At the end, I need the files to produce a pcb with some points to solder the motor, the switcher and the capacitor. There is a 12V plug at the pcb as well. The shape if the pcb is definded and already available as gerber files.