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/admin/themes/grav/templates/statistics.html.twig

@@ -1,15 +0,0 @@
-{% extends 'partials/base.html.twig' %}
-
-{% block messages %}{% endblock %}
-
-{% block content %}
-
-    <div class="admin-block">
-        <h1>
-            {{ "PLUGIN_ADMIN.VIEWS_STATISTICS"|t }}
-        </h1>
-
-        {% include 'partials/messages.html.twig' %}
-    </div>
-{% endblock %}
-