:gear: enforcing usage of env file port

backend/docker-compose.yml

           MYSQL_ROOT_PASSWORD: "${DB_ROOT_PASSWORD}"
           MYSQL_DATABASE: "${DB_NAME}"
         ports:
-          - '3307:3306'
+          - "${DB_PORT}:3306"
 
 volumes:
     siimee_db:

backend/server/manifest.js

                                 user: process.env.DB_USER,
                                 password: process.env.DB_ROOT_PASSWORD,
                                 database: process.env.DB_NAME,
-                                port: 3307,
+                                port: process.env.DB_PORT,
                             },
                         },
                     },