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/services/calendar_service.go

@@ -0,0 +1,134 @@
+package services
+
+import (
+	"context"
+	"encoding/json"
+	"fmt"
+	"log"
+	"os"
+
+	"github.com/breakpilot/school-service/internal/models"
+	"github.com/jackc/pgx/v5/pgxpool"
+)
+
+// CalendarService owns the cal_* tables and the read of the seed snapshot
+// on first boot. Holidays are global (no owner) — same data for every
+// school in a given Bundesland.
+type CalendarService struct {
+	db *pgxpool.Pool
+}
+
+func NewCalendarService(db *pgxpool.Pool) *CalendarService {
+	return &CalendarService{db: db}
+}
+
+// SeedFromSnapshot reads internal/seed/calendar_holidays.json and bulk-inserts
+// every row that doesn't already exist (idempotent via the unique constraint
+// on region+event_type+name_de+start_date). Called once at server start.
+func (s *CalendarService) SeedFromSnapshot(ctx context.Context, path string) error {
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			log.Printf("calendar seed file not found at %s — skipping", path)
+			return nil
+		}
+		return fmt.Errorf("read snapshot: %w", err)
+	}
+
+	var events []models.PublicEvent
+	if err := json.Unmarshal(raw, &events); err != nil {
+		return fmt.Errorf("parse snapshot: %w", err)
+	}
+
+	tx, err := s.db.Begin(ctx)
+	if err != nil {
+		return err
+	}
+	defer tx.Rollback(ctx)
+
+	inserted := 0
+	for _, e := range events {
+		ct, err := tx.Exec(ctx, `
+			INSERT INTO cal_public_event (region, event_type, name_de, name_en, start_date, end_date, source)
+			VALUES ($1, $2, $3, NULLIF($4, ''), $5::date, $6::date, 'OpenHolidaysAPI')
+			ON CONFLICT (region, event_type, name_de, start_date) DO NOTHING
+		`, e.Region, e.EventType, e.NameDe, e.NameEn, e.StartDate, e.EndDate)
+		if err != nil {
+			return fmt.Errorf("insert event: %w", err)
+		}
+		inserted += int(ct.RowsAffected())
+	}
+
+	if err := tx.Commit(ctx); err != nil {
+		return err
+	}
+	log.Printf("calendar seed: %d new events inserted (of %d in snapshot)", inserted, len(events))
+	return nil
+}
+
+// ListHolidays returns all public + school holidays for the given region
+// between from..to (YYYY-MM-DD inclusive).
+func (s *CalendarService) ListHolidays(ctx context.Context, region, from, to string) ([]models.PublicEvent, error) {
+	rows, err := s.db.Query(ctx, `
+		SELECT id, region, event_type, name_de, COALESCE(name_en, ''),
+		       start_date::text, end_date::text, COALESCE(source, ''), created_at
+		FROM cal_public_event
+		WHERE region = $1
+		  AND end_date   >= $2::date
+		  AND start_date <= $3::date
+		ORDER BY start_date, event_type, name_de
+	`, region, from, to)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []models.PublicEvent
+	for rows.Next() {
+		var e models.PublicEvent
+		if err := rows.Scan(&e.ID, &e.Region, &e.EventType, &e.NameDe, &e.NameEn,
+			&e.StartDate, &e.EndDate, &e.Source, &e.CreatedAt); err != nil {
+			return nil, err
+		}
+		out = append(out, e)
+	}
+	return out, nil
+}
+
+// GetConfig returns the per-user calendar config (Bundesland etc.) or nil
+// if the user has not configured one yet.
+func (s *CalendarService) GetConfig(ctx context.Context, userID string) (*models.SchoolCalendarConfig, error) {
+	var c models.SchoolCalendarConfig
+	err := s.db.QueryRow(ctx, `
+		SELECT user_id, bundesland, school_year_start::text, school_year_end::text, created_at, updated_at
+		FROM cal_school_config WHERE user_id = $1
+	`, userID).Scan(&c.UserID, &c.Bundesland, &c.SchoolYearStart, &c.SchoolYearEnd, &c.CreatedAt, &c.UpdatedAt)
+	if err != nil {
+		// pgx returns no-rows error; caller maps to 404.
+		return nil, err
+	}
+	return &c, nil
+}
+
+// UpsertConfig inserts or updates the Bundesland selection.
+func (s *CalendarService) UpsertConfig(ctx context.Context, userID string, req *models.UpsertSchoolCalendarConfigRequest) (*models.SchoolCalendarConfig, error) {
+	var c models.SchoolCalendarConfig
+	err := s.db.QueryRow(ctx, `
+		INSERT INTO cal_school_config (user_id, bundesland, school_year_start, school_year_end)
+		VALUES ($1, $2, NULLIF($3, '')::date, NULLIF($4, '')::date)
+		ON CONFLICT (user_id) DO UPDATE
+		SET bundesland = EXCLUDED.bundesland,
+		    school_year_start = EXCLUDED.school_year_start,
+		    school_year_end   = EXCLUDED.school_year_end,
+		    updated_at = NOW()
+		RETURNING user_id, bundesland, school_year_start::text, school_year_end::text, created_at, updated_at
+	`, userID, req.Bundesland, strOrEmpty(req.SchoolYearStart), strOrEmpty(req.SchoolYearEnd)).
+		Scan(&c.UserID, &c.Bundesland, &c.SchoolYearStart, &c.SchoolYearEnd, &c.CreatedAt, &c.UpdatedAt)
+	return &c, err
+}
+
+func strOrEmpty(s *string) string {
+	if s == nil {
+		return ""
+	}
+	return *s
+}

school-service/internal/services/calendar_service_test.go

@@ -0,0 +1,64 @@
+package services
+
+import (
+	"testing"
+
+	"github.com/breakpilot/school-service/internal/models"
+)
+
+func TestUpsertSchoolCalendarConfigRequest_Validation(t *testing.T) {
+	tests := []struct {
+		name    string
+		req     models.UpsertSchoolCalendarConfigRequest
+		wantErr bool
+	}{
+		{"valid NI", models.UpsertSchoolCalendarConfigRequest{Bundesland: "DE-NI"}, false},
+		{"empty bundesland", models.UpsertSchoolCalendarConfigRequest{Bundesland: ""}, true},
+		{"too long", models.UpsertSchoolCalendarConfigRequest{Bundesland: "DE-NIE"}, true},
+		{"too short", models.UpsertSchoolCalendarConfigRequest{Bundesland: "DE"}, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if (validate.Struct(tt.req) != nil) != tt.wantErr {
+				t.Errorf("unexpected validation outcome for %s", tt.name)
+			}
+		})
+	}
+}
+
+func TestCreateSchoolEventRequest_Validation(t *testing.T) {
+	tests := []struct {
+		name    string
+		req     models.CreateSchoolEventRequest
+		wantErr bool
+	}{
+		{"valid fortbildung", models.CreateSchoolEventRequest{
+			Title: "SCHILF", EventType: "fortbildung",
+			StartDate: "2026-10-01", EndDate: "2026-10-01",
+		}, false},
+		{"missing title", models.CreateSchoolEventRequest{
+			EventType: "fortbildung", StartDate: "2026-10-01", EndDate: "2026-10-01",
+		}, true},
+		{"invalid event type", models.CreateSchoolEventRequest{
+			Title: "X", EventType: "wedding",
+			StartDate: "2026-10-01", EndDate: "2026-10-01",
+		}, true},
+		{"missing dates", models.CreateSchoolEventRequest{
+			Title: "X", EventType: "schulfeier",
+		}, true},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if (validate.Struct(tt.req) != nil) != tt.wantErr {
+				t.Errorf("unexpected validation outcome for %s", tt.name)
+			}
+		})
+	}
+}
+
+func TestNewCalendarService_Constructs(t *testing.T) {
+	s := NewCalendarService(nil)
+	if s == nil {
+		t.Fatal("expected non-nil service")
+	}
+}