Add initial setup for pgAdmin 4 with Docker and Nginx Proxy Manager

- Created .env.example for environment variable configuration.
- Added .gitignore to exclude sensitive files.
- Introduced config_local.py for pgAdmin settings.
- Added docker-compose.portainer.yml for service orchestration.
- Created Dockerfile for custom image building.
- Added README.md with setup instructions and usage guidelines.
- Included servers.json as a template for PostgreSQL server connections.

docker-compose.portainer.yml

@@ -0,0 +1,38 @@
+services:
+  pgadmin:
+    image: dpage/pgadmin4:latest
+    restart: unless-stopped
+    environment:
+      TZ: ${TZ:-UTC}
+      PGADMIN_DEFAULT_EMAIL: ${PGADMIN_DEFAULT_EMAIL}
+      PGADMIN_DEFAULT_PASSWORD: ${PGADMIN_DEFAULT_PASSWORD}
+      PGADMIN_LISTEN_PORT: 80
+      PGADMIN_CONFIG_SERVER_MODE: ${PGADMIN_CONFIG_SERVER_MODE:-True}
+      PGADMIN_CONFIG_MASTER_PASSWORD_REQUIRED: ${PGADMIN_CONFIG_MASTER_PASSWORD_REQUIRED:-True}
+      PGADMIN_CONFIG_UPGRADE_CHECK_ENABLED: ${PGADMIN_CONFIG_UPGRADE_CHECK_ENABLED:-False}
+      PGADMIN_CONFIG_ENHANCED_COOKIE_PROTECTION: ${PGADMIN_CONFIG_ENHANCED_COOKIE_PROTECTION:-True}
+    volumes:
+      - pgadmin_data:/var/lib/pgadmin
+      - ./config_local.py:/pgadmin4/config_local.py:ro
+      - ./servers.json:/pgadmin4/servers.json:ro
+    expose:
+      - "${PGADMIN_PUBLISHED_PORT:-5050}:80"
+    healthcheck:
+      test: ["CMD-SHELL", "python3 -c \"import urllib.request; urllib.request.urlopen('http://127.0.0.1:80/misc/ping').read()\""]
+      interval: 30s
+      timeout: 10s
+      retries: 5
+      start_period: 40s
+    networks:
+      proxy:
+        external: true
+
+networks:
+  internal:
+    driver: bridge
+  proxy:
+    external: true
+
+volumes:
+  pgadmin_data:
+    name: ${PGADMIN_VOLUME_NAME:-pgadmin_data}