feat: declare two SharePoint reference mirrors on Zenith

Preserve the latest working-tree configuration: hourly rclone sync into Algemeen and Projecten, private file creation and a 100-deletion limit per invocation. Only rclone.conf gates the service; the earlier environment-file gate is removed.

Flake evaluation passed. Consent, synchronization and active service state were not checked during cleanup.

modules/hosts/zenith/default.nix

@@ -32,6 +32,7 @@ in
     imports = [
       nixosModules.workstation-base
       nixosModules.laptop-power
+      nixosModules.sharepoint-reference
       ./_hardware.nix
       inputs.nixos-hardware.nixosModules.lenovo-yoga-7-14ARH7-amdgpu
     ];