fix(ci): retry SSH auth check and clarify timeout vs auth errors in Deploy to OVH (#1438)

fix(ci): retry SSH auth check and clarify timeout vs auth errors in Deploy to OVH (#1438)

fix(ci): retry SSH auth check and clarify timeout vs auth-rejection errors

The Deploy to OVH workflow failed intermittently when a transient network
blip caused the SSH connection to time out right after a successful TCP
probe, but the step reported it as an auth failure ("check VPS_SSH_KEY
and VPS_SSH_USER secrets"), which was misleading and caused a false alarm.

Retry the SSH check up to 3 times with backoff on transient failures, but
fail fast without retrying on an actual "Permission denied" rejection, and
report each failure mode with a distinct error message.

Co-authored-by: Pascal HAVELANGE <havelangep@hotmail.com>