feat: add systemd watchdog, OOM detection, disk growth alerting

MEM-01: OOM kill detection via dmesg checks every 5 minutes
MEM-03: Disk growth rate tracking (288 samples over 24h), warns at >1GB/day
MEM-04: Systemd watchdog (WatchdogSec=60, sd_notify::Watchdog every 30s)
        Service Type=notify for proper startup notification

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

image-recipe/configs/archipelago.service

@@ -4,7 +4,7 @@ After=network-online.target archipelago-setup-tor.service
 Wants=network-online.target
 
 [Service]
-Type=simple
+Type=notify
 User=root
 Environment="ARCHIPELAGO_BIND=0.0.0.0:5678"
 Environment="ARCHIPELAGO_DEV_MODE=true"
@@ -12,6 +12,7 @@ ExecStartPre=/bin/bash -c 'mkdir -p /etc/archipelago && echo "ARCHIPELAGO_HOST_I
 ExecStart=/usr/local/bin/archipelago
 Restart=on-failure
 RestartSec=5
+WatchdogSec=60
 
 [Install]
 WantedBy=multi-user.target