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/forms/fields/filepicker/filepicker.html.twig

@@ -1,17 +0,0 @@
-{% embed "forms/fields/select/select.html.twig" %}
-
-    {% block input %}
-        {% if not field.options and value %}
-            {% set field = field|merge({options: {(value): value}}) %}
-        {% endif %}
-        {{ parent() }}
-    {% endblock %}
-
-    {% block global_attributes %}
-        data-grav-filepicker
-        data-name="{{field.name}}"
-        {% if field.preview_images %}data-preview-images{% endif %}
-        data-value="{{value}}"
-        {{ parent() }}
-    {% endblock %}
-{% endembed %}