Mnemonic wallets cannot send

[KayBeSee]

There is a bug where mnemonic wallets cannot send. The broadcast transaction buttons looks like you can send but the button doesn't do anything.

The issue stems from here: https://github.com/Lily-Technologies/lily-wallet/blob/master/src/pages/Send/Onchain/index.tsx#L133

signedDevices is not returning anything. I think this is because we are checking for partial script signatures after the PSBT has been finalized.

I think this might also cause a bug if a finalized, fully-signed PSBT is tried to be broadcast.