Enforce preferences using centralized policy (e.g. group policy, p-list file, etc.)

### Feature description

Possibility to enforce some preferences using group policies, plist file or config file.
In companies, sometimes you want to deploy a config that the user shouldn't be able to change (server name, sync folder name, ...)

The issue names no files, tests, or entry points. Start by mapping the desktop client's existing preference handling and platform configuration support; done requires an agreed policy/configuration mechanism, a defined set of enforceable preferences, and tests showing users cannot override them.

Written by the indexing model from the issue text.