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/app/forms/fields/text.js

@@ -1,13 +0,0 @@
-import $ from 'jquery';
-
-$(document).ready(function() {
-    $('.copy-to-clipboard').click(function(event) {
-        var $tempElement = $('<input>');
-        $('body').append($tempElement);
-        $tempElement.val($(this).prev('input').val()).select();
-        document.execCommand('Copy');
-        $tempElement.remove();
-
-        $(this).attr('data-hint', 'Copied to clipboard!').addClass('hint--left');
-    });
-});