Removes the hardcoded 3m / 15m literals from RemoteUnloaderAdapter and
threads in DistributedConfig.BackendInstallTimeoutOrDefault() and
BackendUpgradeTimeoutOrDefault() at construction. Install now defaults
to 15m (was 3m); cold OCI image pulls on Jetson Wi-Fi routinely blew
past the old ceiling. Scripted messaging client captures the timeout
so tests can assert the configured value actually reaches the NATS
request.
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>