Replaces the {message} interpolation (raw German backend string) with
two distinct error keys: IMPORT_FAILED_NO_SPREADSHEET and
IMPORT_FAILED_INTERNAL. Also removes the {count} parameter from the
done message and adds admin_system_import_status_done_label so the
processed count can be rendered separately at text-base size.
All three locales (de / en / es) updated.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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