Give the technitium LXC a second NIC on the atlashorizon VLAN

Technitium now serves and resolves on 192.168.7.2 as well as its
192.168.0.2 address. The interface was added by hand out of band; this
brings it under management so the next apply does not remove it.

Adopts the module's new nic2 object in place of the VM-only ip2 string.
The submodule bump is a single ref, so it also carries in the Flatcar
module support that the next commit starts using.

Co-Authored-By: Claude Opus 5 <[email protected]>

terraform.tfvars

@@ -145,6 +145,14 @@ nodes = {
         bridge       = "vmbr0"
         ip           = "192.168.0.2/24"
         gw           = "192.168.0.1"
+        # Manually added out-of-band so Technitium can also serve/resolve on
+        # the atlashorizon VLAN; brought under management here to match.
+        nic2 = {
+          nic_name = "eth1"
+          bridge   = "vmbr0"
+          vlan     = 7
+          ip       = "192.168.7.2/24"
+        }
       }
     }
     machines = {