Update pgAdmin configuration by removing the published port from .env.example and docker-compose.portainer.yml, and adjust README.md to reflect changes in service exposure and network settings.

docker-compose.portainer.yml

@@ -16,7 +16,7 @@ services:
       - ./config_local.py:/pgadmin4/config_local.py:ro
       - ./servers.json:/pgadmin4/servers.json:ro
     expose:
-      - "${PGADMIN_PUBLISHED_PORT:-5050}:80"
+      - "80"
     healthcheck:
       test: ["CMD-SHELL", "python3 -c \"import urllib.request; urllib.request.urlopen('http://127.0.0.1:80/misc/ping').read()\""]
       interval: 30s
@@ -24,12 +24,12 @@ services:
       retries: 5
       start_period: 40s
     networks:
-      proxy:
-        external: true
+      - proxy
 
 networks:
   proxy:
     external: true
+    name: ${NPM_NETWORK:-npm_proxy}
 
 volumes:
   pgadmin_data: