refactor: update Docker workflow and configuration for clarity and consistency

docker-compose.yml

@@ -1,14 +1,17 @@
 name: auto-upnp
 services:
   upnp:
-    # image: ghcr.io/vleeuwenmenno/auto-upnp:latest
-    build:
-      context: .
-      dockerfile: Dockerfile
+    image: ghcr.io/vleeuwenmenno/auto-upnp:latest
+    # build:
+    #   context: .
+    #   dockerfile: Dockerfile
     restart: unless-stopped
     network_mode: host
     environment:
       UPNP_DURATION: 86400  # 24 hours in seconds
+      # One-liner
+      # PORTS: [{"port": 80, "protocol": "tcp"}, {"port": 443, "protocol": "tcp"}]
+      # Or multi-line
       PORTS: | 
         [
           {"port": 7777, "protocol": "udp"},