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/contacts/collection/default.html.twig

@@ -1,26 +0,0 @@
-{%- set object_context = object ?? {} -%}
-{%- set object_layout = object_context.layout ?? ('list-' ~ layout) -%}
-
-<div id="flex-objects">
-  <div class="text-center">
-    <input class="form-input search" type="text" placeholder="Search by name, email, etc" />
-    <button class="button button-primary sort asc" data-sort="name">
-      Sort by Name
-    </button>
-  </div>
-
-  <ul class="list">
-    {% for object in collection.filterBy({ published: true }) %}
-      <li>
-        {% render object layout: object_layout with object_context %}
-      </li>
-    {% endfor %}
-  </ul>
-</div>
-
-<script>
-    var options = {
-        valueNames: [ 'name', 'email', 'website', 'entry-extra' ]
-    };
-    var flexList = new List('flex-objects', options);
-</script>