Introduce kind 3043, a new Nostr event that attests an on-chain Bitcoin
payment against a target event or profile. Because every Nostr pubkey
deterministically maps to a Taproot address, any user can receive an
on-chain zap without configuring lud06/lud16 — the zap button now
appears on every post whose author is not the current user.
Publishing flow: sender builds and broadcasts a Bitcoin transaction
paying the recipient's derived Taproot address, then publishes a
kind 3043 event with an `i` tag (`bitcoin:tx:<txid>`), the recipient's
`p`, the target's `e` / `a`, and a self-reported `amount` in sats.
Before displaying or counting a kind 3043 event clients verify the
referenced transaction on-chain and use the sum of outputs paying the
recipient's address as the authoritative amount, capping the sender's
claim at the verified value to prevent spoofing.
Lightning zaps remain available as an opt-in tab inside the zap dialog
whenever the author has a Lightning address configured; otherwise the
dialog is purely on-chain. Defaults favour on-chain: USD amount presets
($1 / $5 / $10 / $25 / $100), fee-speed selection, and a 3-step
form → confirm → success flow mirroring SendBitcoinDialog.
Alex Gleason
bddfe4b838