Invalid signature error from mostrod when creating orders or restoring user

[Catrya]

When using a previously created user (several days old), any interaction with mostrod fails with:

WARN mostrod::app: Error unwrapping gift: Invalid signature

This happens when:

• Creating a new order
• Refreshing/updating the user
• Generating a new user and importing it

Steps to reproduce

1. Use the following test mnemonic: siren total pony spatial fringe submit uniform tape version warm powder blouse
2. Restore the user in the app (you can't)
3. Try to create any order

Mostrod rejects the message with Invalid signature. No useful logs appear on the mobile side.

App debug info:
Restore initialized temp trade key with pubkey:2e2c567eebb54b06ea72f2975a468b5ff0124035e39968ce1a46f2812b008e6a

Related to #276