fix(create-proxmox-resource): auto-generate missing host key before sync

If host-keys/<target>_ssh_host_ed25519_key doesn't exist, run
prepare-host-key.sh to generate it before sync-host-keys.sh runs.
Prevents sync-host-keys.sh from hitting its SKIP/exit-1 path (anchor
in .sops.yaml but no local key) and the downstream disko build failure
when --pre-format-files can't find the key file.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

scripts/proxmox/create-proxmox-resource.sh

@@ -487,6 +487,17 @@ nix_extra_opts
 # --- make sure this target has a registered host key --------------------
 echo
 echo "==> Ensuring host key exists and is registered..."
+_host_keyfile="${repo_root}/host-keys/${flake_target}_ssh_host_ed25519_key"
+if [[ ! -f "$_host_keyfile" ]]; then
+  echo "  No host key found for ${flake_target}; generating one via prepare-host-key.sh..."
+  _prepare_host_key="${repo_root}/scripts/secrets/prepare-host-key.sh"
+  if [[ "$dry_run" -eq 1 ]]; then
+    echo "[dry-run] would run: bash ${_prepare_host_key} ${flake_target}"
+  else
+    bash "$_prepare_host_key" "$flake_target"
+  fi
+fi
+unset _host_keyfile _prepare_host_key
 sync_args=("$flake_target")
 [[ "$dry_run" -eq 1 ]] && sync_args+=(--dry-run)
 bash "$sync_keys" "${sync_args[@]}"