fix: guard dbChat sender fallback against from-me messages

Author: blue-archon

lib/services/backend/actions/chat_actions.dart

@@ -339,8 +339,12 @@ class ChatActions {
       if (dbChat != null) {
         inputMessage.chat.target = dbChat;
 
-        // Fallback: resolve sender against this chat's linked participants
-        if (handleToLink == null && inputMessage.handleId != null && inputMessage.handleId! > 0) {
+        // Fallback: resolve sender against this chat's linked participants (skip
+        // for from-me messages, same mislink reason as the hasSenderHandle guard above).
+        if (handleToLink == null &&
+            !(inputMessage.isFromMe ?? false) &&
+            inputMessage.handleId != null &&
+            inputMessage.handleId! > 0) {
           handleToLink =
               List<Handle>.from(dbChat.handles).firstWhereOrNull((h) => h.originalROWID == inputMessage.handleId);
         }