feat: add editable ordered trail pages

server/migrations/015_seed_trails_from_legacy_categories.sql

@@ -0,0 +1,20 @@
+-- Course categories were previously presented as trilhas but only stored a
+-- label. Turn every existing label into a real ordered trilha without moving
+-- or deleting any course.
+insert into learning_paths (title, description, status, published_at)
+select category.name, '', 'draft', null
+from course_categories category
+where not exists (
+  select 1 from learning_paths path where lower(path.title) = lower(category.name)
+);
+
+insert into learning_path_courses (learning_path_id, course_id, position)
+select path.id, course.id, ranked.position
+from (
+  select id, category, row_number() over (partition by category order by published_at nulls last, title, id)::integer as position
+  from courses
+  where status <> 'archived'
+) ranked
+join courses course on course.id = ranked.id
+join learning_paths path on lower(path.title) = lower(ranked.category)
+on conflict (learning_path_id, course_id) do nothing;