Expose functionality through command line for admin tasks

The main functionality of preparing a repository for registration, as well as sub-parts of it, should be exposed via the command line. This would be useful for:
- Regenerating landing pages (for template modifications).
- Validating zip file consistency.
- Updating metadata when user adds info (e.g., manuscript reference).

Start by mapping the existing repository-registration functionality and its sub-parts. Define command-line entry points for regenerating landing pages, validating zip consistency, and updating metadata; the work is done when each listed administrative task can be run through the command line.

Written by the indexing model from the issue text.