feat(web): add add-member empty-state hint in chat info

web/src/components/ChatInfoPanel.tsx

@@ -712,6 +712,11 @@ export function ChatInfoPanel({ chatId, open, onClose }: Props) {
                       </div>
                     </button>
                   ))}
+                  {searchQuery.trim().replace("@", "").length >= 2 && searchResults.length === 0 ? (
+                    <p className="px-1 py-1 text-xs text-slate-400">
+                      No users available to add (already in chat or banned).
+                    </p>
+                  ) : null}
                 </div>
               </div>
             ) : null}