Function create_sync_storage 

pub async fn create_sync_storage(
    config: &Config,
    key_service: &KeyService,
    encryption_service: &Option<EncryptionService>,
    clock: ClockRef,
) -> Result<EncryptedSyncStorage, String>

Create sync storage from config and credentials.

This is a lighter version of sync::cycle::init_sync that only creates the storage client without starting a sync session or extracting raw DB handles. Used by membership management which only needs storage access.