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/problems/scss/admin.scss

@@ -1,92 +0,0 @@
-@import "variables";
-
-.report-output {
-
-  #admin-main .admin-block & {
-    h1 {
-      margin-top: 2rem;
-    }
-
-    .toast {
-      .btn {
-        float: right;
-        margin-top: -2px;
-        margin-right: 0.5rem;
-        font-size: 90%;
-        padding: 2px 7px;
-        border-radius: 3px;
-      }
-    }
-  }
-
-  ul.problems {
-
-    margin: 1rem 0;
-    list-style: none;
-    padding: 0;
-
-    h5 {
-      margin: 0;
-    }
-
-    li.menu {
-      margin-bottom: 1rem;
-      box-shadow: 0 10px 20px -10px rgba(0,0,0,0.2);
-    }
-
-    .toast {
-      font-size: 1rem;
-      padding: 0.5rem 1.5rem;
-
-      .btn {
-        margin-left: 1rem;
-        text-decoration: none !important;
-        i {
-          margin-right: 0.3rem;
-        }
-      }
-    }
-
-    ul.details {
-      list-style: none;
-      padding-left: 0;
-      padding-bottom: 1rem;
-
-      li {
-        padding-left: 1.5rem;
-        padding-right: 1.5rem;
-      }
-
-      code {
-        font-size: 90%;
-        line-height: 1.2;
-        padding: .1rem .2rem;
-        border-radius: .1rem;
-        vertical-align: middle;
-      }
-
-      .menu-item {
-        margin-top: .5rem !important;
-        padding-top: 0.5rem;
-
-        &:first-child {
-          border: none;
-        }
-      }
-
-      .menu-badge {
-        padding: 0;
-        display: inline;
-        float: right;
-
-        .label {
-          font-size: 1rem;
-          height: 1.5rem;
-          width: 1.5rem;
-          line-height: 1.5rem;
-          border-radius: 3px;
-        }
-      }
-    }
-  }
-}