fix: update database connection settings in docker-compose and database service

backend/services/database.js

@@ -8,6 +8,7 @@ const pool = mysql
     user: process.env.DB_USER,
     password: process.env.DB_PASSWORD,
     database: process.env.DB_NAME,
+    port: process.env.DB_PORT,
   })
   .promise();
 

docker-compose.yml

@@ -23,7 +23,8 @@ services:
       - proxynet
       - borrow_system-internal
     environment:
-      DB_HOST: 127.0.0.1
+      DB_HOST: mysql
+      DB_PORT: 3306
       DB_USER: root
       DB_PASSWORD: ${DB_PASSWORD}
       DB_NAME: borrow_system