fix(zaps): downgrade "Zap Request not found" log from error to debug

Receipts (kind 9735) frequently arrive before their matching zap-request
(kind 9734) is in LocalCache when we are subscribed to receipt relays but
not the zapper's outbox. That race is expected and not actionable from a
user's perspective, yet the previous Log.e wrote a full stack-aiding
error line — including the entire receipt JSON — to logcat for every
unmatched receipt, often six or more times per id within a 15s window.

Downgrade to Log.d so the message stays available for debugging while
no longer flooding error logs in production benchmark runs.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

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

@@ -1673,7 +1673,7 @@ object LocalCache : ILocalCache, ICacheProvider {
             val zapRequest = event.zapRequest?.id?.let { getNoteIfExists(it) }
 
             if (zapRequest == null || zapRequest.event !is LnZapRequestEvent) {
-                Log.e("ZP") { "Zap Request not found. Unable to process Zap {${event.toJson()}}" }
+                Log.d("ZP") { "Zap Request not found. Unable to process Zap {${event.toJson()}}" }
                 return false
             }