chore: Update deploy workflow and Dockerfile for backend

Update the deploy workflow and Dockerfile for the backend. Add the missing `docker compose` command in the `build-backend` step of the deploy workflow and include the `npm start` command in the Dockerfile to start the backend server. These changes ensure correct building and deployment of the backend.

.github/workflows/deploy.yml

@@ -42,4 +42,4 @@ jobs:
             git fetch origin
             git checkout deploy
             git pull
-            docker compose -f docker-compose.yml up | tee docker-compose.log
+            docker compose -f docker-compose.yml up -d --build | tee docker-compose.log