fix self-chat

Sources/Shared/Models/AppModel.swift

@@ -1460,6 +1460,14 @@ final class AppModel: ObservableObject {
     }
 
     func encryptionEnabled(for jid: String) -> Bool {
+        // A conversation with the account's own bare JID is a self-chat.
+        // OMEMO to oneself is meaningless and would force MartinOMEMO to build
+        // a cryptographically invalid self-session (see
+        // `LumaOMEMOStore.removeSessionWithOwnDevice`), producing messages
+        // that later fail to decrypt. Always send self-chat plaintext.
+        if let account, jid.lowercased() == account.normalizedJID {
+            return false
+        }
         return encryptionPreference(for: jid).resolved(globalEnabled: globalEncryptionEnabled)
     }