Implement CSV/JSON import and export for domains, notification groups and tags (with masking for sensitive channel data), including size/format validation, in-memory CSV building, and logging. Add tag transfer and bulk transfer actions (admin-only). Introduce a new update system: Add UpdateController and UpdateService, migration 025_add_update_system_v1.1.3.sql, and installer changes to include the new migration and version handling; provide endpoints to check, apply, rollback and configure updates. Update helpers and UI bits: add getUpdateBadgeInfo in LayoutHelper, update notification icons/redirects, and add getMaxUploadSize in ViewHelper. Misc: add NotificationGroup::findByName, tweak .gitignore backups path, and update related views and routes.
