* fix(settings): require server-side 2fa for sensitive changes
* fix(lint): group third-party imports separately from local (goimports)
golangci-lint goimports flagged setting.go and setting_security_test.go because xlzd/gotp and gorm.io/gorm were mixed into the github.com/mhsanaei/3x-ui local-prefix group. Move them into the third-party group so the local imports stand alone.