Fix ETCP timestamp overflow bug and enable epoll for Linux

lib/u_async.c

@@ -399,8 +399,7 @@ void* uasync_add_socket(struct UASYNC* ua, int fd, socket_callback_t read_cbk, s
         ev.events = 0;
         if (read_cbk) ev.events |= EPOLLIN;
         if (write_cbk) ev.events |= EPOLLOUT;
-        // Use edge-triggered mode for better performance
-        ev.events |= EPOLLET;
+        // Use level-triggered mode (default) for compatibility with UDP sockets
         ev.data.ptr = &ua->sockets->sockets[index];
         
         if (epoll_ctl(ua->epoll_fd, EPOLL_CTL_ADD, fd, &ev) < 0) {