Each readiness probe crosses the real SSH tunnel (desktop -> remote),
so its 1000ms deadline left no room for links with RTT above roughly
that, e.g. satellite or in-flight wifi. Every attempt failed on the
per-request timeout before a response could arrive, and the connection
never succeeded even though the tunnel and remote server were healthy.

Raise the probe deadline to 8s so a slow link only makes connecting
slower, not impossible, while leaving the overall 20s connect budget
alone.

Fixes #7733