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/pages/page/multilang.js

@@ -1,22 +0,0 @@
-import $ from 'jquery';
-
-$('[name="task"][value="saveas"], [name="task"][value="switchlanguage"]').on('mousedown touchstart', (event) => {
-    let fields = ['lang', 'redirect'];
-    let element = $(event.currentTarget);
-    let form = $(`#${element.attr('form')}`);
-
-    if (!form.length) { return; }
-    fields.forEach((field) => {
-        let value = element.attr(field);
-        if (!value) { return; }
-        let input = form.find(`[name="data[${field}]"]`);
-        if (!input.length) {
-            input = $(`<input type="hidden" name="data[${field}]" value="" />`);
-            form.append(input);
-        }
-
-        input.val(value);
-    });
-
-    return true;
-});