fix: prevent form submission during IME composition

[rickychen-infinirc]

Fix issue with Enter key handling during Chinese (and other IME-based) text input

Add detection for IME composition state using event.isComposing flag Add fallback check for keyCode 229 which indicates IME processing Prevent message submission when Enter is pressed during active IME composition Allow normal Enter behavior for confirming IME selections Maintains existing Shift+Enter functionality for line breaks

Before:

https://github.com/user-attachments/assets/2685e0b9-9a5f-43c7-9d4b-10569b697a70

After:

https://github.com/user-attachments/assets/272563fc-760a-4c6b-b35e-d834d1d7d218