feat: add admin screens, permissions and navigation

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.

lang/en/lang.yaml

@@ -1 +1,97 @@
-{}
+plugin:
+    name: BM studies
+    description: Courses, timetable, deadlines, readings and materials of the BM master's programme.
+permissions:
+    access_courses: Manage courses and readings
+    access_schedule: Manage meetings, class sessions and deadlines
+    access_materials: Manage materials and tags
+navigation:
+    courses: Courses
+    readings: Readings
+    meetings: Meetings
+    sessions: Class sessions
+    deadlines: Deadlines
+    materials: Materials
+    tags: Tags
+common:
+    title: Title
+    description: Description
+    notes: Notes
+    course: Course
+    source: Source
+    url: URL
+    sort_order: Sort order
+    created_at: Created
+    none: — none —
+    date_comment: A date in the YYYY-MM-DD form, such as 2026-10-03.
+    datetime_comment: Date and time in Polish time, such as 2026-10-03 08:00.
+forms:
+    wyklad: Lecture
+    cwiczenia: Tutorial
+    konwersatorium: Conversatorium
+    seminarium: Seminar
+    inne: Other
+courses:
+    title: Courses
+    form: Course
+    name: Name
+    form_type: Form
+    code: Code
+    lecturer: Lecturer
+    semester: Semester
+    ects: ECTS
+    assessment: Assessment
+    assessment_comment: Such as egzamin or zaliczenie na ocenę.
+    elective_group: Elective group
+    elective_group_comment: Courses with the same value are alternatives to choose from, such as specjalnosc.
+    syllabus_url: Syllabus URL
+meetings:
+    title: Meetings
+    form: Meeting
+    number: Meeting number
+    starts_on: From
+    ends_on: To
+sessions:
+    title: Class sessions
+    form: Class session
+    meeting: Meeting
+    starts_at: Starts
+    ends_at: Ends
+    room: Room
+    kind: Kind
+    is_online: Online
+deadlines:
+    title: Deadlines
+    form: Deadline
+    due_at: Due
+    kind: Kind
+deadline_kinds:
+    zaliczenie: Credit
+    egzamin: Exam
+    praca: Paper
+    organizacyjne: Administrative
+    inne: Other
+readings:
+    title: Readings
+    form: Reading
+    author: Author
+    is_required: Required
+materials:
+    title: Materials
+    form: Material
+    type: Type
+    body: Body (Markdown)
+    body_comment: A note in Markdown.
+    published_at: Published
+    published_at_comment: Leave empty for a draft that students do not see. Such as 2026-10-03 08:00.
+    tags: Tags
+material_types:
+    pdf: PDF
+    notatka: Note
+    link: Link
+    inne: Other
+tags:
+    title: Tags
+    form: Tag
+    name: Name
+    slug: Slug

lang/pl/lang.yaml

@@ -0,0 +1,97 @@
+plugin:
+    name: Studia BM
+    description: Przedmioty, plan zajęć, terminarz, lektury i materiały studiów magisterskich BM.
+permissions:
+    access_courses: Zarządzanie przedmiotami i lekturami
+    access_schedule: Zarządzanie zjazdami, zajęciami i terminarzem
+    access_materials: Zarządzanie materiałami i tagami
+navigation:
+    courses: Przedmioty
+    readings: Lektury
+    meetings: Zjazdy
+    sessions: Zajęcia
+    deadlines: Terminarz
+    materials: Materiały
+    tags: Tagi
+common:
+    title: Tytuł
+    description: Opis
+    notes: Uwagi
+    course: Przedmiot
+    source: Źródło
+    url: Adres URL
+    sort_order: Kolejność
+    created_at: Utworzono
+    none: — brak —
+    date_comment: Data w formacie RRRR-MM-DD, np. 2026-10-03.
+    datetime_comment: Data i godzina czasu polskiego, np. 2026-10-03 08:00.
+forms:
+    wyklad: Wykład
+    cwiczenia: Ćwiczenia
+    konwersatorium: Konwersatorium
+    seminarium: Seminarium
+    inne: Inne
+courses:
+    title: Przedmioty
+    form: Przedmiot
+    name: Nazwa
+    form_type: Forma zajęć
+    code: Kod
+    lecturer: Prowadzący
+    semester: Semestr
+    ects: ECTS
+    assessment: Forma zaliczenia
+    assessment_comment: Np. egzamin, zaliczenie na ocenę.
+    elective_group: Grupa do wyboru
+    elective_group_comment: Przedmioty o tej samej wartości są alternatywami do wyboru, np. specjalnosc.
+    syllabus_url: Sylabus (URL)
+meetings:
+    title: Zjazdy
+    form: Zjazd
+    number: Numer zjazdu
+    starts_on: Od
+    ends_on: Do
+sessions:
+    title: Zajęcia
+    form: Zajęcia
+    meeting: Zjazd
+    starts_at: Początek
+    ends_at: Koniec
+    room: Sala
+    kind: Rodzaj
+    is_online: Zdalnie
+deadlines:
+    title: Terminarz
+    form: Termin
+    due_at: Termin
+    kind: Rodzaj
+deadline_kinds:
+    zaliczenie: Zaliczenie
+    egzamin: Egzamin
+    praca: Praca
+    organizacyjne: Organizacyjne
+    inne: Inne
+readings:
+    title: Lektury
+    form: Lektura
+    author: Autor
+    is_required: Obowiązkowa
+materials:
+    title: Materiały
+    form: Materiał
+    type: Typ
+    body: Treść (Markdown)
+    body_comment: Notatka w Markdownie.
+    published_at: Opublikowano
+    published_at_comment: Puste pole to szkic, niewidoczny dla studentów. Np. 2026-10-03 08:00.
+    tags: Tagi
+material_types:
+    pdf: PDF
+    notatka: Notatka
+    link: Link
+    inne: Inne
+tags:
+    title: Tagi
+    form: Tag
+    name: Nazwa
+    slug: Slug