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/_badges.scss

@@ -1,60 +0,0 @@
-// Badges
-.badge {
-  position: relative;
-  white-space: nowrap;
-
-  &[data-badge],
-  &:not([data-badge]) {
-    &::after {
-      background: $primary-color;
-      background-clip: padding-box;
-      border-radius: .5rem;
-      box-shadow: 0 0 0 .1rem $bg-color-light;
-      color: $light-color;
-      content: attr(data-badge);
-      display: inline-block;
-      transform: translate(-.05rem, -.5rem);
-    }
-  }
-  &[data-badge] {
-    &::after {
-      font-size: $font-size-sm;
-      height: .9rem;
-      line-height: 1;
-      min-width: .9rem;
-      padding: .1rem .2rem;
-      text-align: center;
-      white-space: nowrap;
-    }
-  }
-  &:not([data-badge]),
-  &[data-badge=""] {
-    &::after {
-      height: 6px;
-      min-width: 6px;
-      padding: 0;
-      width: 6px;
-    }
-  }
-
-  // Badges for Buttons
-  &.btn {
-    &::after {
-      position: absolute;
-      top: 0;
-      right: 0;
-      transform: translate(50%, -50%);
-    }
-  }
-
-  // Badges for Avatars
-  &.avatar {
-    &::after {
-      position: absolute;
-      top: 14.64%;
-      right: 14.64%;
-      transform: translate(50%, -50%);
-      z-index: $zindex-1;
-    }
-  }
-}