fix(forgejo-runner): support generated/unattended mode and configurable runner labels

- Export app-specific variables (var_forgejo_instance, var_forgejo_runner_token,
  var_runner_labels) in ct script so they survive lxc-attach into the container
- Replace nonexistent prompt_input_required/show_missing_values_warning calls
  with standard read prompts that skip when variables are pre-set
- Add hard error when no runner token is provided
- Make runner labels configurable via var_runner_labels instead of hardcoded
- Update default runner image from node:20-bookworm to node:22-bookworm (Node 22 LTS)

ct/forgejo-runner.sh

@@ -18,6 +18,12 @@ var_unprivileged="${var_unprivileged:-1}"
 var_nesting="${var_nesting:-1}"
 var_keyctl="${var_keyctl:-1}"
 
+# App-specific variables (not in build.func whitelist)
+# Export so they survive lxc-attach into the container
+export var_forgejo_instance="${var_forgejo_instance:-}"
+export var_forgejo_runner_token="${var_forgejo_runner_token:-}"
+export var_runner_labels="${var_runner_labels:-}"
+
 header_info "$APP"
 variables
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