chore: update configuration settings

.env.example

@@ -1,12 +1,5 @@
-# DATABASE
-DB_URL="postgresql://${DB_USER}:${DB_PASSWORD}@${DB_HOST}/pingvin-share?schema=public"
-DB_USER=postgres
-DB_PASSWORD=postgres
-DB_HOST=db:5432
-
 # GENERAL
 APP_URL=http://localhost:3000
-BACKEND_URL=http://backend:8080
 SHOW_HOME_PAGE=true
 ALLOW_REGISTRATION=true
 MAX_FILE_SIZE=1000000000