Add registrar CSV sync export/import flow with preview and selection controls

[maricavor]

Summary

• Implemented registrar CSV sync end-to-end in admin area: CSV export from index, CSV import page, preview step, and apply step with create-or-update behavior.
• Added reusable CSV sync UI partials and i18n strings, including field selection controls, preview summary/table, and export action panel.
• Extended importer reliability by supporting both comma- and semicolon-delimited CSV files and stabilizing preview→apply file handoff via tokenized session storage.

Key Behavior

• Export now supports selected registrar rows from index with configurable CSV field list.
• Import flow supports:
• upload + selectable fields,
• preview with created/updated/unchanged/error counts,
• apply with per-row processing and summary flash.
• Import parsing accepts both , and ; CSV delimiters.
• Apply step reuses the previewed file through token-based storage to avoid missing-file errors.