fix known_hosts ownership, ssh dir creation, and root user guard

setup.sh

@@ -100,9 +100,10 @@ case "$KEY_CHOICE" in
 esac
 
 info "Scanning hub host key..."
-sudo -u armbian ssh-keyscan -H "$HUB_HOST" >> "$SSH_DIR/known_hosts" 2>/dev/null
+sudo -u armbian touch "$SSH_DIR/known_hosts"
 chown armbian:armbian "$SSH_DIR/known_hosts"
 chmod 600 "$SSH_DIR/known_hosts"
+sudo -u armbian ssh-keyscan -H "$HUB_HOST" >> "$SSH_DIR/known_hosts" 2>/dev/null
 
 header "Testing SSH Connection"
 info "Testing connection to $HUB_HOST..."