Refactor code structure and remove redundant sections for improved readability and maintainability

docker-compose.yml

@@ -1,8 +1,6 @@
-version: '3.8'
-
 services:
   app:
-    image: node:18
+    image: node:20
     working_dir: /usr/src/app
     volumes:
       - ./:/usr/src/app
@@ -10,6 +8,8 @@ services:
       - "3000:3000"
     restart: unless-stopped
     environment:
-      - NODE_ENV=production
-      - PORT=3000
-    command: sh -c "npm install && npm start"
+      - PORT=${PORT:-3000}
+      - ADMIN_USERNAME=${ADMIN_USERNAME}
+      - ADMIN_PASSWORD=${ADMIN_PASSWORD}
+      - ADMIN_SESSION_SECRET=${ADMIN_SESSION_SECRET}
+    command: sh -c "npm install && npm run build && npm start"