Mettre à jour configuration par défaut pour utiliser template Ubuntu 24.04 LTS et configurer LINSTOR comme backend stockage pour fiabilité et performance améliorées.
Added VM configuration objects for all three nodes:
- k3s_server_1_config: 6 cores, 12GB RAM, 100G disk
- k3s_server_2_config: 6 cores, 12GB RAM, 100G disk
- etcd_witness_config: 2 cores, 2GB RAM, 20G disk
Removed undeclared 'management_bridge' variable that was causing
warnings in terraform plan.
This allows terraform plan to execute successfully in CI with
the example configuration file.
