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/form/templates/forms/fields/date/date.html.twig

@@ -1,8 +0,0 @@
-{% extends "forms/field.html.twig" %}
-
-{% block input_attributes %}
-    type="date"
-    {% if field.validate.min %}min="{{ field.validate.min }}"{% endif %}
-    {% if field.validate.max %}max="{{ field.validate.max }}"{% endif %}
-    {{ parent() }}
-{% endblock %}