Activate User key mode encryption from UI

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Is your feature request related to a problem? Please describe.
User key encryption needs to be explicitly activated by calling ./occ encryption:disable-master-key.
https://docs.nextcloud.com/server/25/admin_manual/configuration_files/encryption_details.html#key-type-user-key

Describe the solution you'd like
User key encryption can be activated from the Admin / Settings page
For example in the Server-side encryption section:
https://docs.nextcloud.com/server/25/admin_manual/configuration_files/encryption_configuration.html#enabling-encryption

Describe alternatives you've considered
None

Additional context
Some hosting providers do not provide access to the command line, making it impossible to enable User key encryption

Start with the Admin/Settings Server-side encryption section and the existing ./occ encryption:disable-master-key entry point, using the linked encryption documentation to understand the current flow. Done means administrators can activate User key encryption from the UI for hosting environments without command-line access, with the existing encryption behavior preserved.