Fix MOTD port 443 detection (check service not iptables)

iptables requires root to read NAT rules. Instead check if the
iptables-restore service is enabled, which indicates 443 redirect
was configured.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

rpi/setup.sh

@@ -314,7 +314,8 @@ if systemctl is-active --quiet stegasoo 2>/dev/null; then
     PI_IP=$(hostname -I | awk '{print $1}')
     # Check if HTTPS and port 443 are configured
     if systemctl show stegasoo -p Environment 2>/dev/null | grep -q "STEGASOO_HTTPS_ENABLED=true"; then
-        if iptables -t nat -L PREROUTING 2>/dev/null | grep -q "dpt:https.*5000"; then
+        # Check for port 443 redirect (iptables-restore service means 443 is configured)
+        if systemctl is-enabled --quiet iptables-restore 2>/dev/null; then
             STEGASOO_URL="https://$PI_IP"
         else
             STEGASOO_URL="https://$PI_IP:5000"