[Feature] Freeze / Read-only server mode for backups

[apparle]

I have searched the existing feature requests, both open and closed, to make sure this is not a duplicate request.

• Yes

The feature

Quoting from the backup guide:

A backup of Immich should contain both the database and the asset files. When backing these up it's possible for them to get out of sync, potentially resulting in broken assets after you restore.
The best way of dealing with this is to stop the immich-server container while you take a backup. If nothing is changing then the backup will always be in sync.

As recommended I usually stop all the containers before backup and then start them again after backup. But if the backup is over a network (for offsite backup) or involves a whole system backup (many files, multiple services involved) it can take a long time for the backup to completely. This is especially true because Immich's backups are bursty -- most days it's only a few photos but on trips there's a LOT of photos uploaded to immich -- consequently assets to be backed up are suddenly a large number, and immich has a long downtime while this happens. And if there's users over multiple timezones, finding a good time slot for this downtime to not be disruptive to users is difficult.

Can we add a "freeze" mode where a backup service can tell immich_server (through a command or a script or an API) to enter a frozen state and not accept new uploads / changes until it receives "unfreeze" command. The backup services can trigger this mode before/after backups and keep everything in sync. And all this while, read-only access to immich with basic app / browsing abilities is permitted.
Is something like this possible?

Platform

• Server
• Web
• Mobile