blocks: pass keypair instead of privkey to avoid pubkey gen

Generating a pubkey is quite slow, so pass a keypair instead of privkey

damus/ContentView.swift

@@ -59,11 +59,11 @@ enum Sheets: Identifiable {
 enum FilterState : Int {
     case posts_and_replies = 1
     case posts = 0
-    
+
     func filter(ev: NostrEvent) -> Bool {
         switch self {
         case .posts:
-            return ev.known_kind == .boost || !ev.is_reply(nil)
+            return ev.known_kind == .boost || !ev.is_reply(.empty)
         case .posts_and_replies:
             return true
         }