A regular smart relay will work just fine if it runs on line voltage. You definitely need to check this by measuring the voltage. Then just tie into the existing circuit and replace the neutral wire nut with a Wago to get a neutral connection for the relay.

Why would you ask Bard something like this? LLMs are not meant to be used for questions like this.

Anyway, without knowing exactly how your switches are wired: keep the traveler wires as-is. You will need to wire up your Shelly in-between the light fixture and the switch that is connected to the fixture. Just connect SW to the load wire of the switch and O to your light fixture. The existing wiring takes care of the 3-way function.