fix: add m.server_notice icon case to getRoomIconSrc

Server notice rooms were falling through to the default hash/lock icon
in the room list. Now return Icons.Warning before any other type checks.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/app/utils/room.ts

@@ -263,6 +263,8 @@ export const getRoomIconSrc = (
   roomType?: string,
   joinRule?: JoinRule,
 ): IconSrc => {
+  if (roomType === 'm.server_notice') return icons.Warning;
+
   if (roomType === RoomType.Space) {
     if (joinRule === JoinRule.Public) return icons.SpaceGlobe;
     if (