Feature Request: Add support for listing device error logs

[davefiddes]

libopeninv now has the ability to list device error logs via CANopen SDO. It would be useful to have this facility available in the can-backend.

The device side implementation can be found here: https://github.com/jsphuebner/libopeninv/blob/3a9c05946de6fab557ec099b9e47a48b946524c0/src/cansdo.cpp#L207C1-L232C5

The OpenInverter CAN Tool client implementation: https://github.com/davefiddes/openinverter-can-tool/blob/de21805aba60db8b847693ec417bc08a8ae88f56/src/openinverter_can_tool/oi_node.py#L482

The web UI expects to be able to execute an "errors" command at the following URL:
http://inverter.local/cmd?cmd=errors

this outputs a plain text string with the following format:

[1]: STOP - GATEDRIVEINITFAIL
[1]: STOP - GATEDRIVEFAULT
[540]: DERATE - OILPUMPFAULT

The number in square brackets is the time in ticks (10ms on stm32-sine, 1000ms on Stm32-vcu) since power on that the error occurred.