Phase 9b: Schul-Events CRUD + Schuljahres-Rollover

Backend (school-service):
  - calendar_events.go — Create/List/Delete on cal_school_event with
    UUID[] handling for affected_class_ids. Default lead-days [7,1]
    if caller omits the array.
  - calendar_rollover.go — single-transaction promotion: graduating
    classes (grade >= 13) get deleted first so the +1 update doesn't
    bump them to invalid grade 14. defaultSchoolYearDates() picks the
    next Aug-Jul pair when the caller doesn't specify.
  - Handlers + routes: GET/POST /calendar/events,
    DELETE /calendar/events/:id, POST /calendar/school-year-rollover.

Frontend (studio-v2):
  - EventModal: form with Title / Typ / Datum/Zeit / unterrichtsfrei /
    Beschreibung / Sichtbarkeit + Notification-Checkboxen. Per-Type
    Farb-Mapping in types.ts.
  - DayDetail: Modal das beim Klick auf einen Kalender-Tag aufgeht und
    Feiertage + Schulferien + Schul-Events fuer diesen Tag listet,
    inkl. Loeschen-Button pro Event.
  - RolloverWizard: zwei-Schritt-Dialog mit Datums-Auswahl + Tipp-
    Bestaetigung ("SCHULJAHR WECHSELN") gegen versehentliche Auslo-
    sung, danach Ergebnis-Card mit promoted/graduated-Counts.
  - MonthView gewinnt onDayClick + onAddEvent + onRollover Props,
    rendert farb-codierte Punkte fuer School-Events am Tagesrand.
  - Page laed Events parallel mit Holidays und reicht alle Handler
    nach unten.

Tests:
  - Go: 3 neue Tests fuer defaultSchoolYearDates + parseClassIDs.
    Validator-Test fuer CreateSchoolEventRequest existiert bereits.
    80 Subtests gesamt, alle gruen.
  - Playwright: mockCalendarApi gewinnt Routes fuer events GET/POST/
    DELETE und school-year-rollover. 6 neue Tests (EventModal open,
    submit, DayDetail open, Rollover-Trigger, Confirm-Schutz,
    Ergebnis-Anzeige).

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

school-service/internal/services/calendar_service_test.go

@@ -62,3 +62,41 @@ func TestNewCalendarService_Constructs(t *testing.T) {
 		t.Fatal("expected non-nil service")
 	}
 }
+
+func TestDefaultSchoolYearDates_FallbackFormat(t *testing.T) {
+	// No override → deterministic YYYY-MM-DD strings with end > start.
+	start, end := defaultSchoolYearDates(nil)
+	if len(start) != 10 || len(end) != 10 {
+		t.Fatalf("expected YYYY-MM-DD strings, got %q %q", start, end)
+	}
+	if end <= start {
+		t.Errorf("end %q must be after start %q", end, start)
+	}
+}
+
+func TestDefaultSchoolYearDates_ExplicitOverride(t *testing.T) {
+	s, e := "2030-09-01", "2031-06-30"
+	req := &models.SchoolYearRolloverRequest{NewYearStart: &s, NewYearEnd: &e}
+	gotS, gotE := defaultSchoolYearDates(req)
+	if gotS != s || gotE != e {
+		t.Errorf("override ignored: got %q/%q want %q/%q", gotS, gotE, s, e)
+	}
+}
+
+func TestParseClassIDs_AcceptsValidAndRejectsGarbage(t *testing.T) {
+	good := []string{"00000000-0000-0000-0000-000000000001", "00000000-0000-0000-0000-000000000002"}
+	out, err := parseClassIDs(good)
+	if err != nil || len(out) != 2 {
+		t.Fatalf("expected 2 parsed UUIDs, got %v err=%v", out, err)
+	}
+
+	if _, err := parseClassIDs([]string{"not-a-uuid"}); err == nil {
+		t.Errorf("expected error for invalid uuid")
+	}
+
+	// Empty strings are silently dropped (curl convenience).
+	out, err = parseClassIDs([]string{"", "00000000-0000-0000-0000-000000000003", ""})
+	if err != nil || len(out) != 1 {
+		t.Errorf("expected 1 parsed UUID, got %v err=%v", out, err)
+	}
+}