chore: 환경 변수 APP_PORT를 PORT로 변경

Author: JHyeok

.env.example

@@ -1,6 +1,6 @@
 # APP
+PORT=3000
 NODE_ENV=development
-APP_PORT=3000
 
 # DATABASE
 DB_HOST=localhost

src/main.ts

@@ -16,7 +16,7 @@ async function bootstrap() {
 
   setupSwagger(app);
 
-  const port = configService.get<number>('APP_PORT');
+  const port = configService.get<number>('PORT');
   const env = configService.get<string>('NODE_ENV');
   await app.listen(port);