fix(desktop): classify failed catalog backups as preservation errors

A failed backup write surfaced as a generic write-temporary-file or
replace-catalog-file error, and the warning logged the raw decrypt cause.
Map the backup write to preserve-undecryptable-catalog and log only the
decrypt error's tag.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
a4df9e92eeJulius Marminge committed on 10/22/2026, 8:35:16 AMparent248ab74

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