fix(bolt12): honor NONZAP zaps as a receiptless BOLT12 payment

A NONZAP (pay-without-receipt) zap must not publish a public 9736. sendBolt12Zap
now settles the offer over NWC without binding an intent or emitting a receipt
when the zap type is NONZAP, matching bolt11 NONZAP privacy.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SpgpWLKzgD7vS9Fs4CXTR3

amethyst/src/main/java/com/vitorpamplona/amethyst/model/Account.kt

@@ -1445,6 +1445,18 @@ class Account(
         onError: (Int, String?) -> Unit,
         onProcessed: () -> Unit,
     ) {
+        // NONZAP means "pay, but publish no receipt" — settle the offer without binding
+        // a zap intent or emitting a 9736, matching the privacy of a bolt11 NONZAP.
+        if (zapType == LnZapEvent.ZapType.NONZAP) {
+            sendNwcRequest(PayMethod.create("bitcoin:?lno=$offer", amountMillisats)) { response ->
+                scope.launch {
+                    if (response is IErrorResponseLike) onError(R.string.bolt12_payment_failed, response.errorMessage())
+                    onProcessed()
+                }
+            }
+            return
+        }
+
         val anonymous = zapType == LnZapEvent.ZapType.ANONYMOUS
         // The 9737 intent and the 9736 zap MUST be signed by the same key. An anonymous
         // zap uses a fresh ephemeral key so it carries no `P` tag and isn't traceable.