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/flex-objects/app/list/index.js

@@ -1,19 +0,0 @@
-import Vue from 'vue';
-import VueEvents from 'vue-events';
-import App from './App.vue';
-
-Vue.use(VueEvents);
-
-const ID = '#flex-objects-list';
-const element = document.querySelector(ID);
-
-if (element) {
-    const initialStore = element.dataset.initialStore;
-
-    new Vue({ // eslint-disable-line no-new
-        el: ID,
-        render: h => h(App, {
-            props: {initialStore}
-        })
-    });
-}