[sBTC DR] Ensure sBTC bridge works with deployed sBTC DR

[netrome]

While the sBTC bridge application supports sBTC OP_RETURN deposits and withdrawals already, it needs to be adjusted to point to the right asset contract after we've deployed it in #85.

Definition of done

The sBTC bridge application has been updated to work with the new sBTC DR asset contract, and we've verified the deposit and withdrawal flows through it.

[friedger]

Depends on leather-io/extension#4223