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_rollover.go

@@ -0,0 +1,85 @@
+package services
+
+import (
+	"context"
+	"fmt"
+	"time"
+
+	"github.com/breakpilot/school-service/internal/models"
+)
+
+// RolloverSchoolYear advances every tt_class for this user by one grade
+// level, removes graduating classes (grade > 13), and updates the
+// cal_school_config school-year dates. Operates as a single transaction.
+//
+// Stammdaten (teachers, subjects, rooms, periods) bleiben unveraendert —
+// es aendern sich nur Klassen-Stufen.
+func (s *CalendarService) RolloverSchoolYear(ctx context.Context, userID string, req *models.SchoolYearRolloverRequest) (*models.SchoolYearRolloverResult, error) {
+	newStart, newEnd := defaultSchoolYearDates(req)
+
+	tx, err := s.db.Begin(ctx)
+	if err != nil {
+		return nil, err
+	}
+	defer tx.Rollback(ctx)
+
+	// 1. Remove the graduating cohort first so they don't get bumped to 14.
+	gradRes, err := tx.Exec(ctx, `
+		DELETE FROM tt_class WHERE created_by_user_id = $1 AND grade_level >= 13
+	`, userID)
+	if err != nil {
+		return nil, fmt.Errorf("delete graduating: %w", err)
+	}
+
+	// 2. Promote everyone else.
+	promRes, err := tx.Exec(ctx, `
+		UPDATE tt_class SET grade_level = grade_level + 1
+		WHERE created_by_user_id = $1
+	`, userID)
+	if err != nil {
+		return nil, fmt.Errorf("promote classes: %w", err)
+	}
+
+	// 3. Update the school-year dates in the config (creates a row if the
+	// user never picked a Bundesland — but that's an edge case; in normal
+	// flow the wizard has run before rollover).
+	_, err = tx.Exec(ctx, `
+		UPDATE cal_school_config
+		SET school_year_start = $1::date,
+		    school_year_end = $2::date,
+		    updated_at = NOW()
+		WHERE user_id = $3
+	`, newStart, newEnd, userID)
+	if err != nil {
+		return nil, fmt.Errorf("update config: %w", err)
+	}
+
+	if err := tx.Commit(ctx); err != nil {
+		return nil, err
+	}
+
+	return &models.SchoolYearRolloverResult{
+		ClassesPromoted:  int(promRes.RowsAffected()),
+		ClassesGraduated: int(gradRes.RowsAffected()),
+		NewYearStart:     newStart,
+		NewYearEnd:       newEnd,
+	}, nil
+}
+
+// defaultSchoolYearDates returns the dates from the request if both set,
+// otherwise the next school year starting Aug 1 of "this year or next"
+// and ending Jul 31 the year after.
+func defaultSchoolYearDates(req *models.SchoolYearRolloverRequest) (string, string) {
+	if req != nil && req.NewYearStart != nil && req.NewYearEnd != nil {
+		return *req.NewYearStart, *req.NewYearEnd
+	}
+	now := time.Now()
+	startYear := now.Year()
+	// If we're past August, the "new" year refers to the next calendar year.
+	if int(now.Month()) >= 8 {
+		startYear++
+	}
+	start := time.Date(startYear, 8, 1, 0, 0, 0, 0, time.UTC)
+	end := time.Date(startYear+1, 7, 31, 0, 0, 0, 0, time.UTC)
+	return start.Format("2006-01-02"), end.Format("2006-01-02")
+}