feat: configure environment variables, CORS, and PostgreSQL database settings for backend-frontend integration

.env.example

@@ -9,6 +9,7 @@ DB_PORT=5432
 DEBUG=True
 SECRET_KEY=django-secret-key
 ALLOWED_HOSTS=localhost,127.0.0.1
+CORS_ALLOWED_ORIGINS=http://localhost:5173,http://127.0.0.1:5173
 
 # EMAIL
 EMAIL_HOST=localhost
@@ -16,3 +17,4 @@ EMAIL_PORT=1025
 
 # FRONTEND
 VITE_API_URL=http://localhost:8000
+FRONTEND_PORT=5173