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/forms/fields/userinfo/userinfo.html.twig

@@ -1,19 +0,0 @@
-{% extends "forms/field.html.twig" %}
-
-{% block field %}
-<div class="form-field grid user-details">
-    <div class="form-label block size-1-3">
-        {% include 'partials/userinfo-avatar.html.twig' %}
-    </div>
-    <div class="form-data block size-2-3">
-        <h2>{{ data.fullname }}</h2>
-        <h5>
-        <a href="mailto:{{ data.email }}">{{ data.email }}</a>
-        {% if data.title %}
-        - {{ data.title }}
-        {% endif %}
-        </h5>
-        {% include 'partials/userinfo-avatar-credit.html.twig' %}
-    </div>
-</div>
-{% endblock %}