Make community logos white and larger in widget header

- NEMAR: brain fill changed to white (was dark blue)
- EEGLAB/SCCN: all fills changed to white (was navy)
- Logo img size increased from 28px to 32px in avatar circle

Author: neuromechanist

frontend/osa-chat-widget.js

@@ -253,8 +253,8 @@
     }
 
     .osa-chat-avatar img {
-      width: 28px;
-      height: 28px;
+      width: 32px;
+      height: 32px;
       object-fit: contain;
       border-radius: 50%;
     }