Phase 9a: Schulkalender — Bundesland-Auswahl + Monatsansicht mit Ferien

Backend (school-service):
  - cal_public_event (region, event_type, name_de, name_en, start/end,
    UNIQUE(region, event_type, name_de, start_date)) — global snapshot.
  - cal_school_config (user_id PRIMARY KEY, bundesland, school year dates).
  - cal_school_event — Schul-eigene Termine; CRUD folgt in 9b.
  - GET /calendar/holidays?region=&from=&to= — Range-Query against
    cal_public_event, ordered by start_date.
  - GET / PUT /calendar/config — upsert Bundesland per User.
  - SeedFromSnapshot reads internal/seed/calendar_holidays.json on every
    boot; idempotent via the unique constraint. Async goroutine so the
    HTTP server starts immediately even if the seed file is large.

Data source:
  - scripts/calendar-snapshot.sh ruft openholidaysapi.org fuer alle 16
    Bundeslaender x 3 Schuljahre und schreibt
    school-service/internal/seed/calendar_holidays.json (854 Events,
    Stand Schuljahre 2026-2028).
  - Dockerfile kopiert das seed/-Verzeichnis ins Image, damit die
    Container-Datenbank beim ersten Start gefuellt wird.

Frontend (studio-v2):
  - /schulkalender Page mit Gradient + Blobs wie /stundenplan und
    /korrektur — gleicher Visual-Style.
  - BundeslandWizard: zeigt alle 16 Laender als Dropdown, speichert
    bei Klick die Config und switcht zur Monatsansicht.
  - MonthView: 6-Wochen-Grid Mo-So, Feiertage rose-toned, Schulferien
    amber-toned, heutiges Datum mit Indigo-Ring. Prev/Next/Heute
    Navigation.
  - lib/schulkalender/api.ts re-uses the stundenplan JWT helper so
    auth-mode wechselt nicht.
  - Sidebar bekommt einen Schulkalender-Eintrag (Icon mit Datum-Dots,
    Pfad /schulkalender) in allen 26 Sprachen.

Tests:
  - Go: 3 neue Validator-Tests (Bundesland len=5, EventType oneof,
    Pflichtfelder). 77 Tests gesamt, alle gruen.
  - Playwright: e2e/schulkalender.spec.ts mit Wizard, Save-Flow,
    MonthView-Render, Heute-Button, Sidebar-Link. Hermetisch via
    mockCalendarApi.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

school-service/internal/models/calendar.go

@@ -0,0 +1,80 @@
+package models
+
+import (
+	"time"
+
+	"github.com/google/uuid"
+)
+
+// PublicEvent is a holiday or school-vacation row imported from
+// OpenHolidaysAPI. Global (no owner) — same for every school per region.
+type PublicEvent struct {
+	ID        uuid.UUID `json:"id" db:"id"`
+	Region    string    `json:"region" db:"region"`           // e.g. "DE-NI"
+	EventType string    `json:"event_type" db:"event_type"`   // public_holiday | school_holiday
+	NameDe    string    `json:"name_de" db:"name_de"`
+	NameEn    string    `json:"name_en,omitempty" db:"name_en"`
+	StartDate string    `json:"start_date" db:"start_date"`   // YYYY-MM-DD
+	EndDate   string    `json:"end_date" db:"end_date"`
+	Source    string    `json:"source,omitempty" db:"source"`
+	CreatedAt time.Time `json:"created_at" db:"created_at"`
+}
+
+// SchoolCalendarConfig stores the Bundesland selection for one school
+// (= one Rektor account). One row per user.
+type SchoolCalendarConfig struct {
+	UserID          uuid.UUID `json:"user_id" db:"user_id"`
+	Bundesland      string    `json:"bundesland" db:"bundesland"`            // DE-NI ...
+	SchoolYearStart *string   `json:"school_year_start,omitempty" db:"school_year_start"`
+	SchoolYearEnd   *string   `json:"school_year_end,omitempty" db:"school_year_end"`
+	CreatedAt       time.Time `json:"created_at" db:"created_at"`
+	UpdatedAt       time.Time `json:"updated_at" db:"updated_at"`
+}
+
+// SchoolEvent is a user-managed event (Fortbildung, Schulfeier, …).
+type SchoolEvent struct {
+	ID                   uuid.UUID   `json:"id" db:"id"`
+	CreatedByUserID      uuid.UUID   `json:"created_by_user_id" db:"created_by_user_id"`
+	Title                string      `json:"title" db:"title"`
+	Description          string      `json:"description,omitempty" db:"description"`
+	EventType            string      `json:"event_type" db:"event_type"`
+	IsSchoolFree         bool        `json:"is_school_free" db:"is_school_free"`
+	StartDate            string      `json:"start_date" db:"start_date"`
+	EndDate              string      `json:"end_date" db:"end_date"`
+	StartTime            *string     `json:"start_time,omitempty" db:"start_time"`
+	EndTime              *string     `json:"end_time,omitempty" db:"end_time"`
+	AffectedClassIDs     []uuid.UUID `json:"affected_class_ids" db:"affected_class_ids"`
+	VisibleToParents     bool        `json:"visible_to_parents" db:"visible_to_parents"`
+	NotifyParents        bool        `json:"notify_parents" db:"notify_parents"`
+	NotifyStudents       bool        `json:"notify_students" db:"notify_students"`
+	NotificationLeadDays []int       `json:"notification_lead_days" db:"notification_lead_days"`
+	CreatedAt            time.Time   `json:"created_at" db:"created_at"`
+	UpdatedAt            time.Time   `json:"updated_at" db:"updated_at"`
+}
+
+// Request DTOs
+
+// UpsertSchoolCalendarConfigRequest sets or updates the Bundesland for the
+// authenticated user. Both school-year dates are optional (defaults to the
+// running year based on today's date).
+type UpsertSchoolCalendarConfigRequest struct {
+	Bundesland      string  `json:"bundesland" binding:"required,len=5"`
+	SchoolYearStart *string `json:"school_year_start,omitempty"`
+	SchoolYearEnd   *string `json:"school_year_end,omitempty"`
+}
+
+type CreateSchoolEventRequest struct {
+	Title                string   `json:"title" binding:"required"`
+	Description          string   `json:"description"`
+	EventType            string   `json:"event_type" binding:"required,oneof=fortbildung schulfeier klassenfahrt projekttag eltern_info andere"`
+	IsSchoolFree         bool     `json:"is_school_free"`
+	StartDate            string   `json:"start_date" binding:"required"`
+	EndDate              string   `json:"end_date" binding:"required"`
+	StartTime            *string  `json:"start_time,omitempty"`
+	EndTime              *string  `json:"end_time,omitempty"`
+	AffectedClassIDs     []string `json:"affected_class_ids"`
+	VisibleToParents     bool     `json:"visible_to_parents"`
+	NotifyParents        bool     `json:"notify_parents"`
+	NotifyStudents       bool     `json:"notify_students"`
+	NotificationLeadDays []int    `json:"notification_lead_days"`
+}