chore: update postgres service configuration in CI workflow to use dynamic port mapping

.github/workflows/ci.yml

@@ -11,8 +11,6 @@ env:
   DB_NAME: piku_test_db
   DB_USER: test
   DB_PASSWORD: password123
-  DB_HOST: postgres
-  DB_PORT: 5432
 
 jobs:
   setup-environment:
@@ -75,7 +73,12 @@ jobs:
           POSTGRES_DB: ${{ env.DB_NAME }}
           POSTGRES_USER: ${{ env.DB_USER }}
           POSTGRES_PASSWORD: ${{ env.DB_PASSWORD }}
+        ports:
+          - 5432
         options: --health-cmd pg_isready --health-interval 10s --health-timeout 5s --health-retries 5
+    env:
+      DB_HOST: 127.0.0.1
+      DB_PORT: ${{ job.services.postgres.ports['5432'] }}
     defaults:
       run:
         working-directory: ./backend