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/changelog.html.twig

@@ -1,21 +0,0 @@
-{% set slug = uri.param('slug') %}
-
-{% set changelog = admin.getChangelog(slug) %}
-
-<section id="ajax" class="changelog">
-    <a href="#" class="remodal-close"></a>
-    {% if changelog %}
-
-        <h1>{{title}} Changelog</h1>
-
-        <div class="changelog-overflow">
-            {% for version, log in changelog %}
-                <h3 id="{{ version | replace({" ": '-'}) }}">v{{ version }}</h3>
-                <h4 title="{{ log.date|date('F jS \\a\\t g:ia') }}">{{ log.date|nicetime }}</h4>
-
-                {{ log.content|markdown|raw }}
-            {% endfor %}
-        </div>
-
-    {% endif %}
-</section>