v1.7.2

updater: shut down cleanly on self-update instead of std::exit

After swapping the binary the updater called std::exit(0) from an IOTMP
worker thread while the io_context threads were still live, so static
destructors ran underneath them and the process aborted (SIGABRT, exit -6);
KeepAlive restarted it but the update path never exited cleanly. Raise
SIGTERM instead to drive the normal shutdown (workers stop, client
disconnect, teardown), then the init system restarts the new binary.