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/user-accounts/object/default.html.twig

@@ -1,17 +0,0 @@
-{% set mailto = object.fullname|default(object.key) ~ ' <' ~ object.email ~ '>' %}
-{% set avatar = object.getAvatarUrl %}
-
-<h2>{{ object.fullname }}</h2>
-<div>
-    {% if object.title %}
-    <div>
-        Role: {{ object.title|e }}
-    </div>
-    {% endif %}
-    {% block avatar %}
-    <img src="{{ avatar|e }}" alt="">
-    {% endblock %}
-    <div>
-        <a href="mailto:{{ mailto|e }}">{{ mailto|e }}</a>
-    </div>
-</div>

plugins/flex-objects/templates/flex/user-accounts/object/list-default.html.twig

@@ -1,27 +0,0 @@
-{% set mailto = object.fullname|default(object.key) ~ ' <' ~ object.email ~ '>' %}
-{% set avatar = object.getAvatarUrl %}
-
-<div class="entry-details">
-    {% if link %}
-    <a href="{{ link|e }}">
-        {{ block('avatar') }}
-    </a>
-    {% else %}
-    {% block avatar %}
-        <img src="{{ avatar|e }}" alt="">
-    {% endblock %}
-    {% endif %}
-    <div>
-        <a href="mailto:{{ mailto|e }}">{{ mailto|e }}</a>
-    </div>
-    {% if object.title %}
-    <div>
-        Role: {{ object.title|e }}
-    </div>
-    {% endif %}
-    {% if link %}
-    <div>
-        <a href="{{ link }}">See Details</a>
-    </div>
-    {% endif %}
-</div>