The material admin form gets the "Na zjazd" picker, every student
material JSON carries meeting_id, and GET /materials accepts meeting=
inside the published-only scope, so the Pulpit hero can list the
zjazd's materials next to its readings.
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).
Seven admin controllers in a "Studia BM" navigation group, guarded by
jz.bm.access_courses, jz.bm.access_schedule and jz.bm.access_materials,
with Polish and English labels. Date and time fields are checked by the
models before a save and answered as 422 on the field.
