From my mislead I put
HAL_PWR_EnterSTANDBYMode() in the code whithout any wakeup behaviour, which made my chip unable to debug via SWD interface. So I can not either erase, upload new code or do anything with this chip.
I have an Aliexpress ST-Link V2 dongle for programing and debug. I connected the terget to the dongle with the following wires:
I hoped that NRST will hold the target from running my broken code, but it is still not programmable and debuggable (I turned Reset behaviour setting to "Connect under reset").
The second thing I tried is to connect BOOT0 pin to VCC while power up. The problem is that my chip is STM32G030F which has BOOT0 and SWCLK on the same pin (PA14). So I tried to power up while PA14 (BOOT0) was connected to VCC and then - I disconnected PA14 from VCC and connected PA14 (SWCLK) to USB dongle. Same thing: no effect.
What else can I do to wake up my chip from standby mode?