Set up backups for media files on block storage

## Summary
Set up backups for uploaded media files stored on block storage.

## Scope
- Identify all media paths stored on DigitalOcean Volume Block Storage.
- Create a scheduled backup or sync job for media files.
- Store backups in selected cloud storage or another durable target.
- Include retention, restore, and integrity-check strategy.
- Ensure backups do not interrupt the running platform.

## Acceptance Criteria
- Media files on block storage are backed up on a schedule.
- Backup destination and retention are documented.
- Restore steps are documented.
- Backup jobs report failures through logs or alerting.

No repository files, tests, or entry points are named. Start by locating the platform configuration and all media paths on DigitalOcean Volume Block Storage, then define the backup job, durable destination, retention, restore procedure, integrity checks, and failure reporting; done means the acceptance criteria are documented and verified without interrupting the platform.

Written by the indexing model from the issue text.