feat: enhance logging configuration and add request logging context

.env.example

@@ -14,6 +14,8 @@ POSTGRES_PORT=5432
 # --- backend settings (see backend/.env.example for full list) ---
 CORS_ORIGINS=http://localhost:3000
 DB_AUTO_MIGRATE=true
+LOG_LEVEL=INFO
+REQUEST_LOG_SLOW_MS=1000
 
 # --- frontend settings ---
 # REQUIRED: Public URL used by the browser to reach the API.