feat: WAN IP Guard - dynamic DNS updater with WhatsApp notifications

Checks public WAN IP every 5 minutes via systemd timer. On change:
- Updates A-records via DirectAdmin API (login key auth)
- Sends WhatsApp notification via wwebjs-api

.env.example

@@ -0,0 +1,16 @@
+# DirectAdmin API credentials
+DA_LOGIN_KEY=your_login_key_here
+DA_USERNAME=your_username
+DA_BASE_URL=https://panel.example.com:2222
+DA_DOMAIN=example.com
+
+# WhatsApp API (wwebjs-api)
+WHATSAPP_API_ENDPOINT=http://localhost:3001
+WHATSAPP_SESSION=your_session
+ADMIN_PHONE=31600000000
+
+# DNS records to update (comma-separated, use domain name for apex)
+DNS_RECORDS=example.com,git,www
+
+# State file path (where to store last known IP)
+STATE_FILE=/var/lib/wan-ip-guard/current_ip