fix(dashboard): translate error messages in Windsurf login flows when i18n keys exist

All Windsurf login error display paths (single/batch/import) now attempt I18n.t() on error strings before rendering. If the error message is a known i18n key (I18n.t(err) !== err), use the translated version; otherwise fall back to the raw error string. Covers toast notifications, status text, result cards, and batch table cells.