fix: correct DATABASE_URL password placeholder in docker-compose.yml

The 'postgres' password was literally written as the masked '***'
placeholder (copy-paste artifact), causing Prisma P1000 auth failures
against the db service. Set it to match POSTGRES_PASSWORD.

docker-compose.yml

@@ -28,7 +28,7 @@ services:
     env_file:
       - .env
     environment:
-      DATABASE_URL: postgresql://postgres:***@db:5432/kcapp?schema=public
+      DATABASE_URL: postgresql://postgres:postgres@db:5432/kcapp?schema=public
       PORT: "3000"
       GOOGLE_APPLICATION_CREDENTIALS: /app/serviceAccount.json
       APP_BASE_URL: http://localhost:3010