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/_typography.scss

@@ -1,128 +0,0 @@
-// Typography
-// Headings
-h1,
-h2,
-h3,
-h4,
-h5,
-h6 {
-  color: inherit;
-  font-weight: 500;
-  line-height: 1.2;
-  margin-bottom: .5em;
-  margin-top: 0;
-}
-.h1,
-.h2,
-.h3,
-.h4,
-.h5,
-.h6 {
-  font-weight: 500;
-}
-h1,
-.h1 {
-  font-size: 2rem;
-}
-h2,
-.h2 {
-  font-size: 1.6rem;
-}
-h3,
-.h3 {
-  font-size: 1.4rem;
-}
-h4,
-.h4 {
-  font-size: 1.2rem;
-}
-h5,
-.h5 {
-  font-size: 1rem;
-}
-h6,
-.h6 {
-  font-size: .8rem;
-}
-
-// Paragraphs
-p {
-  margin: 0 0 $line-height;
-}
-
-// Semantic text elements
-a,
-ins,
-u {
-  text-decoration-skip: ink edges;
-}
-
-abbr[title] {
-  border-bottom: $border-width dotted;
-  cursor: help;
-  text-decoration: none;
-}
-
-kbd {
-  @include label-base();
-  @include label-variant($light-color, $dark-color);
-  font-size: $font-size-sm;
-}
-
-mark {
-  @include label-variant($body-font-color, $highlight-color);
-  border-radius: $border-radius;
-  padding: .05rem;
-}
-
-// Blockquote
-blockquote {
-  border-left: $border-width-lg solid $border-color;
-  margin-left: 0;
-  padding: $unit-2 $unit-4;
-
-  p:last-child {
-    margin-bottom: 0;
-  }
-}
-
-// Lists
-ul,
-ol {
-  margin: $unit-4 0 $unit-4 $unit-4;
-  padding: 0;
-
-  ul,
-  ol {
-    margin: $unit-4 0 $unit-4 $unit-4;
-  }
-
-  li {
-    margin-top: $unit-2;
-  }
-}
-
-ul {
-  list-style: disc inside;
-
-  ul {
-    list-style-type: circle;
-  }
-}
-
-ol {
-  list-style: decimal inside;
-
-  ol {
-    list-style-type: lower-alpha;
-  }
-}
-
-dl {
-  dt {
-    font-weight: bold;
-  }
-  dd {
-    margin: $unit-2 0 $unit-4 0;
-  }
-}