Function map_open_error 

fn map_open_error(error: DatabaseOpenError) -> ImportError

Maps keepass open errors to the credential-vs-corrupt distinction the UI surfaces.

A wrong password/key file surfaces as a key or decryption error (KDBX 3.1 has no key HMAC, so it fails as bad padding). keepass’s CryptographyError isn’t public, so we can’t separate that from genuine corruption — bias both to wrong-credentials; everything else is corrupt/unsupported.