scanAccountsAsync swallows a per-account failure so the remaining accounts can
still scan. That is right for importing, which only adds and updates, but
FindInactiveBooks treats whatever came back as the whole library and reports
every un-liberated book missing from it as no longer in the account. For a
single-account user a login or network failure therefore yields an empty scan,
and 'Remove Books' pre-checks the entire un-liberated library. ImportAccountAsync
already guards itself with 'if (totalCount == 0) return default;'; this path had
no equivalent.
Track which accounts failed and refuse to identify inactive books when any did,
or when a scan returns nothing while books are at stake. Both grids already
catch and report a failed scan with 'Error scanning library. You may still
manually select books to remove', so throwing lands in the right place and
leaves nothing checked.
Also log how many books the scan found absent, so the count behind a removal
prompt is visible after the fact.
Co-authored-by: rmcrackan <rmcrackan@gmail.com>
