feat(11.1-05): add the walkthrough's admin controller, publish command and published_at migration

- make:admin-controller, make:command and make:migration output, finished:
  the Posts controller serves models.Post behind acme.blog.access_posts,
  WinterCMS-style form and list YAML embedded through pact.AdminAssets,
  blog:publish sets published_at by slug with a bound parameter
- the posts route lists published posts only, newest first
- Docker tests migrate an ICU pl-PL database, roll back published_at, serve
  the route and run blog:publish with a published and an opened database
- the page gains the admin controller, console command and added-column
  sections

docs/examples/blog/lang/en/lang.yaml

@@ -1 +1,12 @@
-{}
+plugin:
+    name: Blog
+    description: A simple blog.
+permissions:
+    access_posts: Manage blog posts
+posts:
+    title: Posts
+    post: Post
+    title_field: Title
+    slug: Slug
+    body: Body
+    published_at: Published