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/flex-objects/templates/flex-edit.html.twig

@@ -1,42 +0,0 @@
-{% extends "partials/base.html.twig" %}
-
-{% set object = form.object %}
-{% if object is null %}
-  {% throw 404 'Not Found' %}
-{% endif %}
-
-{% if form.flash.exists() %}
-  {% set draft = true %}
-  {% try %}
-    {% set object = form.updateObject() %}
-  {% catch %}
-  {% endcatch %}
-{% endif %}
-
-{% if header.title %}
-  {% do page.title('Edit ' ~ object.title) %}
-{% endif %}
-
-{% block content %}
-  {% include 'partials/messages.html.twig' ignore missing %}
-
-  <section id="default-page" class="basic-row">
-    <div class="container grid-sm form">
-      {{ page.content()|raw }}
-
-      {#
-      <div class="unsaved-changes d-hide">You have unsaved changes</div>
-      #}
-
-      {% include "forms/form.html.twig" %}
-    </div>
-  </section>
-
-  {% block modals %}
-    {#
-    {% if form.buttons.preview %}
-      {% include 'modals/flex-preview.html.twig' %}
-    {% endif %}
-    #}
-  {% endblock %}
-{% endblock %}