Datepickers on native time.Time / lagoon.Date fields, file uploads on
materials, readings and class sessions managed from the course form
(course_id made nullable).
Dashboard, courses with counters, schedule, meetings, deadlines,
readings with per-user progress (mark and unmark) and paginated
published materials with tags and files, behind golem15.user's
jwt.auth. Responses are built field by field with Warsaw RFC 3339
timestamps; bad query parameters answer 422 in Laravel's shape.