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/handlers/handlers.go

@@ -17,6 +17,7 @@ type Handler struct {
 	certificateService *services.CertificateService
 	aiService          *services.AIService
 	timetableService   *services.TimetableService
+	calendarService    *services.CalendarService
 	solverServiceURL   string
 }
 
@@ -29,6 +30,7 @@ func NewHandler(db *pgxpool.Pool, llmGatewayURL, solverServiceURL string) *Handl
 	certificateService := services.NewCertificateService(db, gradeService, gradebookService)
 	aiService := services.NewAIService(llmGatewayURL)
 	timetableService := services.NewTimetableService(db)
+	calendarService := services.NewCalendarService(db)
 
 	return &Handler{
 		classService:       classService,
@@ -38,10 +40,17 @@ func NewHandler(db *pgxpool.Pool, llmGatewayURL, solverServiceURL string) *Handl
 		certificateService: certificateService,
 		aiService:          aiService,
 		timetableService:   timetableService,
+		calendarService:    calendarService,
 		solverServiceURL:   solverServiceURL,
 	}
 }
 
+// CalendarService exposes the underlying service so main.go can run the
+// one-off seed import after migrations.
+func (h *Handler) CalendarService() *services.CalendarService {
+	return h.calendarService
+}
+
 // Health returns the service health status
 func (h *Handler) Health(c *gin.Context) {
 	c.JSON(http.StatusOK, gin.H{