Fix FLARE_OPERATOR_PORT parsing: replace atoi with strtol + range validation

[Copilot]

FLARE_OPERATOR_PORT was parsed with atoi, which silently returns 0 on invalid input and has no range validation — allowing an invalid port to reach index_server_port without any diagnostic.

Changes

• src/flared/flared.cc
  • Replace atoi with strtol + full error detection (errno, endptr, trailing-char check)
  • Validate parsed port is in range [1, 65535]; emit log_warning and skip override on invalid input
  • Parse once into port_val; reuse static_cast<int>(port_val) for both s.index_server_port and the log_notice line
  • Add <cerrno> to the ENABLE_K8S_OPERATOR include guard

char* endptr = nullptr;
errno = 0;
long port_val = strtol(op_port, &endptr, 10);
if (errno != 0 || endptr == op_port || *endptr != '\0' || port_val < 1 || port_val > 65535) {
    log_warning("K8s operator mode: invalid FLARE_OPERATOR_PORT value '%s', ignoring operator override", op_port);
} else {
    k8s_index_servers.clear();
    cluster::index_server s;
    s.index_server_name = string(op_host);
    s.index_server_port = static_cast<int>(port_val);
    k8s_index_servers.push_back(s);
    log_notice("K8s operator mode: using operator at %s:%d as index server",
        op_host, static_cast<int>(port_val));
}

---

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.