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/cmd/server/main.go

@@ -1,7 +1,9 @@
 package main
 
 import (
+	"context"
 	"log"
+	"os"
 
 	"github.com/breakpilot/school-service/internal/config"
 	"github.com/breakpilot/school-service/internal/database"
@@ -37,6 +39,19 @@ func main() {
 	// Create handler
 	handler := handlers.NewHandler(db.Pool, cfg.LLMGatewayURL, cfg.SolverServiceURL)
 
+	// Calendar seed — idempotent, runs every boot. Snapshot path is bundled
+	// in the Docker image at /app/internal/seed/calendar_holidays.json. Failures
+	// don't block startup; the holiday table is filled lazily next boot.
+	go func() {
+		seedPath := "internal/seed/calendar_holidays.json"
+		if _, err := os.Stat(seedPath); err != nil {
+			seedPath = "/app/internal/seed/calendar_holidays.json"
+		}
+		if err := handler.CalendarService().SeedFromSnapshot(context.Background(), seedPath); err != nil {
+			log.Printf("calendar seed failed: %v", err)
+		}
+	}()
+
 	// Create router
 	router := gin.New()
 	router.Use(gin.Recovery())
@@ -232,6 +247,11 @@ func main() {
 		// Phase 8: exports.
 		api.GET("/timetable/solutions/:id/export.csv", handler.ExportTimetableSolutionCSV)
 		api.GET("/timetable/solutions/:id/export.ics", handler.ExportTimetableSolutionICS)
+
+		// Phase 9a: Schulkalender (holidays + per-user Bundesland config).
+		api.GET("/calendar/holidays", handler.ListCalendarHolidays)
+		api.GET("/calendar/config", handler.GetCalendarConfig)
+		api.PUT("/calendar/config", handler.UpsertCalendarConfig)
 	}
 
 	// Start server