Move plugins to manifest, pin Docker version, add Makefile

- Add plugins.txt listing all plugins for reproducible installs
- Add Makefile with setup/start/stop/install-plugins targets
- Remove user/plugins/ from git tracking
- Pin Docker image to 1.7.49.5-ls244

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

plugins/form/templates/forms/fields/nonce/nonce.html.twig

@@ -1,4 +0,0 @@
-{% set nonce_action = form.getNonceAction() ?? 'form' %}
-{% set nonce_name = form.getNonceName() ?? 'form-nonce' %}
-{% set nonce_value = form.getNonce() %}
-<input type="hidden" name="{{ nonce_name }}" value="{{ nonce_value }}" class="form-nonce-field" data-nonce-action="{{ nonce_action }}" />