Ecash zaps:

- Receiver (R) announces on their nostr profile which mints they're on

- R posts something dope on nostr

- Sender (S) mints P2PK-locked ecash from R's mint to R's nostr pubkey

- S attaches locked ecash to R's post

- Observer (O) sees ecash attached to R's note and verifies P2PK lock ("receiver is R") and DLEQ proof ("ecash is legit").

- O's nostr client shows "1234 sats zapped from S to R"