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/partials/nav-user-details.html.twig

@@ -1,21 +0,0 @@
-<div id="offline-status">
-    <span><i class="fa fa-fw fa-plane"></i> You are offline</span>
-</div>
-{% set flex = grav['flex_objects'] ?? null %}
-{% set user = admin.user %}
-{% if flex and user.hasFlexFeature('user') %}
-    {% set route = flex.adminRoute(user) %}
-{% else %}
-    {% set route = '/user/' ~ user.username %}
-{% endif %}
-
-<div id="admin-user-details">
-    <a href="{{ admin_route(route) }}">
-        {% include 'partials/nav-user-avatar.html.twig' %}
-
-        <div class="admin-user-names">
-            <h4>{{ user.fullname }} {% if user.twofa_enabled and config.plugins.admin.twofa_enabled %}<span class="badge">2FA</span>{% endif %}</h4>
-            <h5>{{ user.title }}</h5>
-        </div>
-    </a>
-</div>