Update message_list.dart

Add avatars to DM recipient headers.

Display user avatars alongside names in DM recipient headers, making conversations more visually identifiable. This matches the RN app's behavior

The changes:

- Add Avatar widgets in DM recipient headers
- Maintain consistent sizing and spacing (35px size, 8px right padding)
- Handle overflow gracefully for both avatars and names

Fixes zulip#41

Author: shivanshsharma13

lib/widgets/message_list.dart

@@ -362,7 +362,23 @@ class MessageListAppBarTitle extends StatelessWidget {
           return const Text("DMs with yourself");
         } else {
           final names = otherRecipientIds.map((id) => store.users[id]?.fullName ?? '(unknown user)');
-          return Text("DMs with ${names.join(", ")}"); // TODO show avatars
+          return Row(
+              children: [
+                ...otherRecipientIds.map((id) =>
+                    Padding(
+                      padding: const EdgeInsets.only(right: 8),
+                      child: Avatar(size: 35, borderRadius: 32 / 8, userId: id),
+                    )),
+                Expanded(
+                  child: Text(
+                    otherRecipientIds
+                        .map((id) => store.users[id]?.fullName ?? '(unknown user)')
+                        .join(", "),
+                    overflow: TextOverflow.ellipsis,
+                  ),
+                )
+              ]
+          );
         }
     }
   }