feat(web): add empty-state hint for banned users filter

web/src/components/ChatInfoPanel.tsx

@@ -783,6 +783,9 @@ export function ChatInfoPanel({ chatId, open, onClose }: Props) {
                       </div>
                     );
                   })}
+                  {bans.length > 0 && filteredBans.length === 0 ? (
+                    <p className="px-1 py-1 text-xs text-slate-400">No banned users match this filter.</p>
+                  ) : null}
                 </div>
               </div>
             ) : null}