terraform: refactor cloud-init to use proxmox_cloud_init_disk resource

Replace SSH upload approach with native proxmox_cloud_init_disk resource
for cleaner, more maintainable cloud-init management.

Changes:
- Use proxmox_cloud_init_disk for all VMs (not just branch-specific ones)
- Include SSH keys, network config, and metadata in cloud-init disk
- Conditionally include NIXOS_FLAKE_BRANCH for VMs with flake_branch set
- Replace ide2 cloudinit disk with cdrom reference to cloud-init disk
- Remove built-in cloud-init parameters (ciuser, sshkeys, etc.)
- Remove cicustom parameter (no longer needed)
- Remove proxmox_host variable (no SSH uploads required)
- Remove .gitignore entry for .generated/ directory

Benefits:
- No SSH access to Proxmox required
- All cloud-init config managed in Terraform
- Consistent approach for all VMs
- Cleaner state management

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

terraform/vms.tf

@@ -32,10 +32,10 @@ locals {
     # "minimal-vm" = {}
     # "bootstrap-verify-test" = {}
     "testvm01" = {
-      ip        = "10.69.13.101/24"
-      cpu_cores = 2
-      memory    = 2048
-      disk_size = "20G"
+      ip           = "10.69.13.101/24"
+      cpu_cores    = 2
+      memory       = 2048
+      disk_size    = "20G"
       flake_branch = "pipeline-testing-improvements"
     }
   }
@@ -104,8 +104,9 @@ resource "proxmox_vm_qemu" "vm" {
     }
     ide {
       ide2 {
-        cloudinit {
-          storage = each.value.storage
+        # Reference the custom cloud-init disk created in cloud-init.tf
+        cdrom {
+          iso = proxmox_cloud_init_disk.ci[each.key].id
         }
       }
     }
@@ -117,18 +118,6 @@ resource "proxmox_vm_qemu" "vm" {
   # Agent
   agent = 1
 
-  # Cloud-init configuration
-  ciuser       = "root"
-  sshkeys      = each.value.ssh_public_key
-  nameserver   = each.value.nameservers
-  searchdomain = each.value.search_domain
-
-  # Network configuration - DHCP or static IP
-  ipconfig0 = each.value.ip != null ? "ip=${each.value.ip},gw=${each.value.gateway}" : "ip=dhcp"
-
-  # Custom cloud-init disk for branch configuration (if flake_branch is set)
-  cicustom = each.value.flake_branch != null ? "user=${each.value.storage}:snippets/cloud-init-${each.key}.yml" : null
-
   # Skip IPv6 since we don't use it
   skip_ipv6 = true