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/datetime/datetime.html.twig

@@ -1,27 +0,0 @@
-{% extends "forms/field.html.twig" %}
-
-{% set value = (value is null ? field.default : value) %}
-{% set default_php_dateformat = admin.guessDateFormat(value) %}
-{% set php_dateformat = field.format ?: (form ? form.object.dateformat : admin.page.dateformat) ?: config.system.pages.dateformat.default ?: default_php_dateformat %}
-{% set js_dateformat = admin.dateformatToMomentJS(php_dateformat) %}
-{% set value = (value is null ? value : value|date(php_dateformat)) %}
-
-{% block input %}
-<div class="form-input-wrapper datetime-picker-wrapper {{ field.size }}">
-    {% set input_value = value is iterable ? value|join(',') : value|string %}
-    <input
-            name="{{ (scope ~ field.name)|fieldName }}"
-            value="{{ input_value }}"
-            {% block input_attributes %}
-                type="text"
-                data-grav-datetime="{{ {'format': js_dateformat} | json_encode | e('html_attr') }}"
-                {% if field.validate.min %}min="{{ (field.validate.min is null ? field.validate.min : field.validate.min|date(php_dateformat)) }}"{% endif %}
-                {% if field.validate.max %}max="{{ (field.validate.max is null ? field.validate.max : field.validate.max|date(php_dateformat)) }}"{% endif %}
-                {{ parent() }}
-            {% endblock %}
-    />
-    <span class="field-icons">
-        <i class="fa fa-fw fa-calendar"></i>
-    </span>
-</div>
-{% endblock %}