OptionalbackupOptionalencryptWhen set, the serialized open bytes are wrapped via encryptWinBoxCdb
before atomic write. salt is optional — omit to let the codec roll a
fresh 32-byte salt per write (the normal path); pin it only in tests that
need byte-exact output. The caller is responsible for matching the source
password (centrs reads it from the loaded CDB's settings).
OptionalnowClock injection for deterministic backup timestamps in tests.
OptionalskipSkip the backup snapshot entirely (used for first-time creation).
Number of
*.bak.*snapshots to keep; older ones are pruned.