feat(prod): configure 'netlab' virtual machine in terraform

Add the configuration for the "netlab" VM in the production environment. This machine is provisioned with:
- OS: Debian
- 8 CPU cores
- 16GB RAM
- 64GB Disk
- Static IP 192.168.1.161

terraform/prod/terraform.tfvars

@@ -33,7 +33,17 @@ admin_ssh_public_key_path = "~/.ssh/keys/id_rsa.pub"
 # Utilisateur par défaut sur les VMs
 default_vm_user = "damien"
 
-virtual_machines = {}
+virtual_machines = {
+  "netlab" = {
+    os      = "debian"
+    cores   = 8
+    memory  = 16384
+    disk_gb = 64
+    ip      = "192.168.1.161"
+    gateway = "192.168.1.254"
+    tags    = ["netlab"]
+  }
+}
 
 #############################
 # Notes de configuration