Add validateDatabasesBackupInput() helper that properly parses all
database backup formats including MongoDB's "db:col1,col2|db2:col3"
and validates each component individually.
- Validate and escape collection names in DatabaseBackupJob
- Replace comma-only split in BackupEdit with format-aware validation
- Add input validation in API create_backup and update_backup endpoints
- Add unit tests for collection name and multi-format validation
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
