Display custom backup error (#446)

## Describe your PR

This PR updates the backup documentation to clarify the behavior of
custom backup configurations with multiple retention policies and
periods. It explains that while the Clever Cloud console does not
display all backups for restoration, users can leverage the CLI to
restore a specific backup.

---------

Co-authored-by: Juju-archy <[email protected]>
Co-authored-by: Clément Nivolle <[email protected]>
Co-authored-by: David Legrand <[email protected]>
Co-authored-by: Julia March <[email protected]>

content/doc/find-help/faq.md

@@ -212,9 +212,10 @@ If a VACUUM operation needs more disk that there is remaining, migrating to the
 
 ## Where are the backups stored?
 
-Clever Cloud store all your backups on [Cellar](https://www.clever-cloud.com/product/cellar-object-storage/). 
-Cellar has a replication system to protect the data stored inside. It creates three copies of your backups, each stored in a different data centers in the PAR region.  
-This way, even if one data center has an accident, your backup are still safe in two different data centers.
+Clever Cloud stores all backups on [Cellar](https://www.clever-cloud.com/product/cellar-object-storage/), a replicated object storage service with three copies distributed across datacenters in the PAR region to ensure durability. Even if one datacenter fails, your backups remain safe.
+
+For custom configurations (for example, multiple retention policies), contact Support. To locate backups not visible in the Console, use [Clever Tools](https://github.com/CleverCloud/clever-tools) with: `clever database backups DATABASE-ID [--format, -F] FORMAT`.  Find more documentation on restoring backups with the CLI [here](https://github.com/CleverCloud/clever-tools/blob/master/docs/addons-backups.md#database-backups).
+
 
 ## I can't create my add-on