fix(chats): handle ChatMessageEncryptedFileHeaderEvent in GiftWrap unwrap

The GiftWrap inner event handler only processed ChatMessageEvent (kind 14)
and ReactionEvent. ChatMessageEncryptedFileHeaderEvent (kind 15) was
silently dropped, so encrypted file attachments never appeared in DMs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

desktopApp/src/jvmMain/kotlin/com/vitorpamplona/amethyst/desktop/Main.kt

@@ -649,6 +649,18 @@ fun MainContent(
                                     )
                                 }
 
+                                is com.vitorpamplona.quartz.nip17Dm.files.ChatMessageEncryptedFileHeaderEvent -> {
+                                    val innerNote = localCache.getOrCreateNote(innerEvent.id)
+                                    val innerAuthor = localCache.getOrCreateUser(innerEvent.pubKey)
+                                    if (innerNote.event == null) {
+                                        innerNote.loadEvent(innerEvent, innerAuthor, emptyList())
+                                    }
+                                    iAccount.chatroomList.addMessage(
+                                        innerEvent.chatroomKey(iAccount.pubKey),
+                                        innerNote,
+                                    )
+                                }
+
                                 is com.vitorpamplona.quartz.nip25Reactions.ReactionEvent -> {
                                     val reactionNote = localCache.getOrCreateNote(innerEvent.id)
                                     val reactionAuthor = localCache.getOrCreateUser(innerEvent.pubKey)