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/partials/form-messages.html.twig

@@ -1,6 +0,0 @@
-{% if form.message %}
-    {% set inline_errors = form.inline_errors is not null ? form.inline_errors : config.plugins.form.inline_errors(false) %}
-    {% set status_mapping = {'success':'green', 'error': 'red', 'warning': 'yellow'} %}
-    {% set message = inline_errors and form.messages ? "GRAV.FORM.VALIDATION_FAIL"|t : form.message %}
-    <div class="notices {{ form.status }} {{ status_mapping[form.status] ?: 'green' }}"><p>{{ message|raw }}</p></div>
-{% endif %}

plugins/form/templates/partials/form-messages.json.twig

@@ -1,3 +0,0 @@
-{% set inline_errors = form.inline_errors is not null ? form.inline_errors : config.plugins.form.inline_errors(false) %}
-{% set message = inline_errors and form.messages ? "GRAV.FORM.VALIDATION_FAIL"|t : form.message %}
-{{ {'status':form.status, 'message':message}|json_encode|raw }}