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/blueprints/config/media.yaml

@@ -1,36 +0,0 @@
-title: PLUGIN_ADMIN.MEDIA
-form:
-  validation: loose
-  fields:
-    'types':
-      name: medias
-      type: list
-      label: PLUGIN_ADMIN.MEDIA_TYPES
-      style: vertical
-      key: extension
-      controls: both
-      collapsed: true
-
-      fields:
-        .extension:
-          type: key
-          label: PLUGIN_ADMIN.FILE_EXTENSION
-        .type:
-          type: text
-          label: PLUGIN_ADMIN.TYPE
-        .thumb:
-          type: text
-          label: PLUGIN_ADMIN.THUMB
-        .mime:
-          type: text
-          label: PLUGIN_ADMIN.MIME_TYPE
-          validate:
-            type: lower
-        .image:
-          type: textarea
-          yaml: true
-          label: PLUGIN_ADMIN.IMAGE_OPTIONS
-          validate:
-            type: yaml
-
-