Changes

This PR adds PgBackRest support to backups. PgBackRest allows for incremental backups, which means that it is much, much more storage efficient for larger databases.

Things I made sure to add:

• API routes
• Notifications for things like backup failures
• A few rudimentary tests
• A basic UI to configure things like compression method (lz4 by default)

If PgBackRest is enabled, instead of requiring an image change, we install PgBackRest into the Postgres container so people can use custom images instead of having to rely on PGBR-specific ones.

Also made sure that functionality works fine in dev mode.

Issues

• fix #7423

/claim #7423