Add NIP-57 Lightning zaps (npub / lightning address / lnurl)

Send a Lightning zap to a nostr npub, a lightning address (name@domain),
or an lnurl. New src/lnurl.js does the resolution half — target → LNURL-pay
params → signed kind-9734 zap request → callback → bolt11 — and the new
zaps feature (src/features/zaps.js) drives the amount/comment UI, then hands
the invoice to the existing Boltz submarine-swap flow via a new
swaps.startLnPay hook, so there's one tested pay/review/confirm/success path.

Routing: a bolt11 is still caught by swaps; an npub still prefers an instant
free Ark zap when Ark can serve it, and only falls through to a Lightning
zap otherwise — ark's "no Ark address" screen also offers an explicit
"Zap over Lightning" fallback (gated on the zaps feature's canLnZap). A real
zap receipt is attributed only when the server advertises allowsNostr and we
know the recipient's pubkey; otherwise it degrades to a plain LNURL-pay.

Nostr seam gains nostrSign (finalize without publishing), nostrProfile
(kind-0 with lud16/lud06), and nostrRelays. Lightning addresses are
debounced in matchSendText since their regex matches mid-typing.

Verified: unit tests for parse/encode/zap-request; a live resolve→signed
9734→payable mainnet bolt11 against coinos; and an in-browser DOM smoke
(zap form + LNURL params over CORS + allowsNostr hint + handoff).

Co-Authored-By: Claude Opus 4.8 <[email protected]>

1 files changed, 19 insertions, 1 deletions

diff --git a/src/features/sync.js b/src/features/sync.js
index 715c789..1e2db41 100644
--- a/src/features/sync.js
+++ b/src/features/sync.js
@@ -3,7 +3,7 @@
 // (used e.g. to DM locked-gift claim codes). Installed onto the core wallet;
 // a build without sync ships none of it and never talks to a relay.
 
-import { NostrSync, getSyncConfig, setSyncConfig, npubOf, syncDtag, deviceDtag, isOurDtag } from '../nostr.js';
+import { NostrSync, getSyncConfig, setSyncConfig, npubOf, syncDtag, deviceDtag, isOurDtag, fetchNostrProfile, PROFILE_RELAYS } from '../nostr.js';
 import { t } from '../i18n.js';
 
 // Keep a published snapshot under the relay's event-size cap. relay.coinos.io
@@ -62,6 +62,24 @@ export function installSyncWallet(wallet) {
       return this.nostr.subscribeEvents(filter, onEvent);
     },
 
+    // Sign an event with our nostr key without publishing (NIP-57 zap request).
+    nostrSign(partial) { return this.nostr ? this.nostr.signEvent(partial) : null; },
+
+    // Fetch a pubkey's profile (name/picture + lud16/lud06 for zaps) from the
+    // broad profile relays — independent of whether cross-device sync is on.
+    async nostrProfile(pkHex) {
+      if (this.offline) return null;
+      return fetchNostrProfile(pkHex);
+    },
+
+    // Relays to advertise in a zap request so we can later find the receipt:
+    // our sync relays plus the broad profile relays.
+    nostrRelays() {
+      const sync = getSyncConfig();
+      const base = sync.enabled ? sync.relays : [];
+      return [...new Set([...base, ...PROFILE_RELAYS])].slice(0, 8);
+    },
+
     // Pull the latest state from Nostr; apply it if it's newer than what we have.
     // Returns true if state was applied (so the caller can skip a full scan).
     async syncFromNostr() {