Backups may be generated with out-of-date database data

BackupService & BackupController is serving up the wrong database backup zip when asked for the latest one. This means backups are being generated where the filesystem and database do not match. This could lead to data loss when restoring.

Specifically, if the delta between two backups in milliseconds is greater than Integer.MAX_VALUE which is about 25 days, the comparison of last modified dates for two files will return an invalid value, ordering will fail and the wrong database backup file will be designated as the latest one.