Add Silent Payment Receive Optionality

[Gudnessuche]

Given the open-source nature of this project, and keeping with the cypher punk ethos, it's only prudent that Seed Signer had silent payment support as a hardware wallet.

I believe that since the Silent Payment BIP has been merged into core, it only makes sense that Seed Signer lead in proliferating SP usage.

[kdmukai]

There's nothing on the SeedSigner side required for SP receive (well, aside from generating the shareable SP payment code/address, which was already prototyped here). Since you already covered sending in #633, the missing piece would be SPENDING silent payment utxos.