feat(export): CSV export for bookings and customers

GET /v1/export/bookings.csv (optional from/to bounds) and
/v1/export/customers.csv — UTF-8 with BOM for Excel, labels resolved
at export time, buffered responses so auth failures stay JSON.
Export buttons on the bookings and customers pages.

Generated with [Devin](https://devin.ai)

Co-Authored-By: Devin <158243242+devin-ai-integration[bot]@users.noreply.github.com>

apps/backend/internal/export/service.go

@@ -0,0 +1,174 @@
+package export
+
+import (
+	"context"
+	"encoding/csv"
+	"errors"
+	"io"
+	"time"
+
+	"bookra/apps/backend/internal/db"
+	"bookra/apps/backend/internal/domain"
+)
+
+var ErrTenantMembership = errors.New("tenant membership not found")
+
+// utf8BOM lets Excel detect the encoding for Czech diacritics.
+var utf8BOM = []byte{0xEF, 0xBB, 0xBF}
+
+const customerPageSize = 500
+
+type Service struct {
+	repo db.Repository
+}
+
+func NewService(repo db.Repository) *Service {
+	return &Service{repo: repo}
+}
+
+func (s *Service) tenantFor(ctx context.Context, principal domain.Principal) (db.TenantRecord, error) {
+	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
+	if err != nil {
+		return db.TenantRecord{}, ErrTenantMembership
+	}
+	return membership.Tenant, nil
+}
+
+// WriteBookingsCSV streams every tenant booking in [from, to) as CSV rows.
+// Service labels resolve to service names for appointments and session titles
+// for classes, matching how the rest of the app labels them.
+func (s *Service) WriteBookingsCSV(ctx context.Context, principal domain.Principal, w io.Writer, from, to time.Time) error {
+	tenant, err := s.tenantFor(ctx, principal)
+	if err != nil {
+		return err
+	}
+
+	bookings, err := s.repo.ListBookingsByTenantBetween(ctx, tenant.ID, from, to)
+	if err != nil {
+		return err
+	}
+	services, err := s.repo.ListServicesByTenant(ctx, tenant.ID)
+	if err != nil {
+		return err
+	}
+	sessions, err := s.repo.ListClassSessionsByTenant(ctx, tenant.ID, from, 10000)
+	if err != nil {
+		return err
+	}
+	staff, err := s.repo.ListStaffByTenant(ctx, tenant.ID)
+	if err != nil {
+		return err
+	}
+	locations, err := s.repo.ListLocationsByTenant(ctx, tenant.ID)
+	if err != nil {
+		return err
+	}
+
+	serviceNames := make(map[string]string, len(services))
+	for _, service := range services {
+		serviceNames[service.ID] = service.Name
+	}
+	sessionTitles := make(map[string]string, len(sessions))
+	for _, session := range sessions {
+		sessionTitles[session.ID] = session.Title
+	}
+	staffNames := make(map[string]string, len(staff))
+	for _, member := range staff {
+		staffNames[member.ID] = member.DisplayName
+	}
+	locationNames := make(map[string]string, len(locations))
+	for _, location := range locations {
+		locationNames[location.ID] = location.Name
+	}
+
+	if _, err := w.Write(utf8BOM); err != nil {
+		return err
+	}
+	out := csv.NewWriter(w)
+	defer out.Flush()
+
+	if err := out.Write([]string{
+		"reference", "status", "customer_name", "customer_email", "customer_phone",
+		"service", "staff", "location", "starts_at", "ends_at", "created_at", "notes",
+	}); err != nil {
+		return err
+	}
+	for _, booking := range bookings {
+		label := ""
+		if booking.ServiceID != nil {
+			label = serviceNames[*booking.ServiceID]
+		}
+		if booking.ClassSessionID != nil {
+			label = sessionTitles[*booking.ClassSessionID]
+		}
+		staffName := ""
+		if booking.StaffID != nil {
+			staffName = staffNames[*booking.StaffID]
+		}
+		locationName := ""
+		if booking.LocationID != nil {
+			locationName = locationNames[*booking.LocationID]
+		}
+		if err := out.Write([]string{
+			booking.Reference,
+			booking.Status,
+			booking.CustomerName,
+			booking.CustomerEmail,
+			booking.CustomerPhone,
+			label,
+			staffName,
+			locationName,
+			booking.StartsAt.UTC().Format(time.RFC3339),
+			booking.EndsAt.UTC().Format(time.RFC3339),
+			booking.CreatedAt.UTC().Format(time.RFC3339),
+			booking.Notes,
+		}); err != nil {
+			return err
+		}
+	}
+	return out.Error()
+}
+
+// WriteCustomersCSV streams the tenant's full customer list, paging through
+// the repository in bounded chunks.
+func (s *Service) WriteCustomersCSV(ctx context.Context, principal domain.Principal, w io.Writer) error {
+	tenant, err := s.tenantFor(ctx, principal)
+	if err != nil {
+		return err
+	}
+
+	if _, err := w.Write(utf8BOM); err != nil {
+		return err
+	}
+	out := csv.NewWriter(w)
+	defer out.Flush()
+
+	if err := out.Write([]string{"name", "email", "phone", "status", "created_at"}); err != nil {
+		return err
+	}
+	for offset := 0; ; offset += customerPageSize {
+		page, err := s.repo.ListCustomersByTenant(ctx, tenant.ID, customerPageSize, offset)
+		if err != nil {
+			return err
+		}
+		for _, customer := range page {
+			phone := ""
+			if customer.Phone != nil {
+				phone = *customer.Phone
+			}
+			if err := out.Write([]string{
+				customer.Name,
+				customer.Email,
+				phone,
+				customer.Status,
+				customer.CreatedAt.UTC().Format(time.RFC3339),
+			}); err != nil {
+				return err
+			}
+		}
+		if len(page) < customerPageSize {
+			break
+		}
+	}
+	return out.Error()
+}

apps/backend/internal/export/service_test.go

@@ -0,0 +1,149 @@
+package export
+
+import (
+	"bytes"
+	"context"
+	"encoding/csv"
+	"strings"
+	"testing"
+	"time"
+
+	"bookra/apps/backend/internal/db"
+	"bookra/apps/backend/internal/domain"
+)
+
+var demoPrincipal = domain.Principal{Subject: "demo-owner", Role: "owner"}
+
+const demoTenantID = "5d6b3551-0a3e-4b86-bdf0-e9df20a47148"
+
+func readCSV(t *testing.T, buf *bytes.Buffer) [][]string {
+	t.Helper()
+	records, err := csv.NewReader(strings.NewReader(strings.TrimPrefix(buf.String(), "\ufeff"))).ReadAll()
+	if err != nil {
+		t.Fatalf("parse csv: %v\n%s", err, buf.String())
+	}
+	return records
+}
+
+func TestWriteBookingsCSVResolvesLabelsAndEscapes(t *testing.T) {
+	repo := db.NewMemoryRepository()
+	serviceID := "d5d76a61-3d49-467c-8dd4-bf61ee754e39" // "Signature treatment"
+	staffID := "6936c444-c7d0-4a7d-b596-a9b72d2f4fc0"   // "Demo Stylist"
+	locationID := "659f1cc0-a850-46d6-b3b8-cb15d55d8daf"
+	_, err := repo.CreateBooking(context.Background(), db.CreateBookingParams{
+		TenantID:      demoTenantID,
+		ServiceID:     &serviceID,
+		StaffID:       &staffID,
+		LocationID:    &locationID,
+		CustomerName:  "Novák, Jiří",
+		CustomerEmail: "[email protected]",
+		CustomerPhone: "+420111222333",
+		StartsAt:      time.Now().Add(24 * time.Hour),
+		EndsAt:        time.Now().Add(25 * time.Hour),
+		Status:        "confirmed",
+		Reference:     "BK-CSV-1",
+		ManageToken:   "tok",
+		Notes:         "note with \"quotes\"",
+	})
+	if err != nil {
+		t.Fatalf("create booking: %v", err)
+	}
+
+	var buf bytes.Buffer
+	svc := NewService(repo)
+	from := time.Now().Add(-time.Hour)
+	to := time.Now().Add(72 * time.Hour)
+	if err := svc.WriteBookingsCSV(context.Background(), demoPrincipal, &buf, from, to); err != nil {
+		t.Fatalf("write csv: %v", err)
+	}
+
+	if !bytes.HasPrefix(buf.Bytes(), utf8BOM) {
+		t.Fatal("expected UTF-8 BOM for Excel compatibility")
+	}
+	records := readCSV(t, &buf)
+	if len(records) != 2 {
+		t.Fatalf("expected header + 1 row, got %d rows", len(records))
+	}
+	row := records[1]
+	if row[0] != "BK-CSV-1" || row[1] != "confirmed" {
+		t.Fatalf("unexpected reference/status: %v", row[:2])
+	}
+	if row[2] != "Novák, Jiří" {
+		t.Fatalf("expected escaped customer name, got %q", row[2])
+	}
+	if row[5] != "Signature treatment" || row[6] != "Demo Stylist" || row[7] != "Main Studio" {
+		t.Fatalf("expected resolved labels, got service=%q staff=%q location=%q", row[5], row[6], row[7])
+	}
+	if row[11] != `note with "quotes"` {
+		t.Fatalf("expected escaped notes, got %q", row[11])
+	}
+}
+
+func TestWriteBookingsCSVRangeExcludesOutOfWindow(t *testing.T) {
+	repo := db.NewMemoryRepository()
+	_, err := repo.CreateBooking(context.Background(), db.CreateBookingParams{
+		TenantID:      demoTenantID,
+		CustomerName:  "Far Future",
+		CustomerEmail: "[email protected]",
+		StartsAt:      time.Now().Add(200 * 24 * time.Hour),
+		EndsAt:        time.Now().Add(200*24*time.Hour + time.Hour),
+		Status:        "confirmed",
+		Reference:     "BK-CSV-FAR",
+		ManageToken:   "tok",
+	})
+	if err != nil {
+		t.Fatalf("create booking: %v", err)
+	}
+
+	var buf bytes.Buffer
+	svc := NewService(repo)
+	from := time.Now().Add(-time.Hour)
+	to := time.Now().Add(24 * time.Hour) // far-future booking outside
+	if err := svc.WriteBookingsCSV(context.Background(), demoPrincipal, &buf, from, to); err != nil {
+		t.Fatalf("write csv: %v", err)
+	}
+	for _, record := range readCSV(t, &buf) {
+		if record[0] == "BK-CSV-FAR" {
+			t.Fatal("expected range to exclude far-future booking")
+		}
+	}
+}
+
+func TestWriteCustomersCSVPagesAndStrips(t *testing.T) {
+	repo := db.NewMemoryRepository()
+	var buf bytes.Buffer
+	svc := NewService(repo)
+	if err := svc.WriteCustomersCSV(context.Background(), demoPrincipal, &buf); err != nil {
+		t.Fatalf("write csv: %v", err)
+	}
+	records := readCSV(t, &buf)
+	if len(records) < 2 {
+		t.Fatalf("expected header + seeded customers, got %d rows", len(records))
+	}
+	if records[0][0] != "name" || records[0][4] != "created_at" {
+		t.Fatalf("unexpected header: %v", records[0])
+	}
+	found := false
+	for _, record := range records[1:] {
+		if record[0] == "Alice Johnson" && record[1] == "[email protected]" {
+			found = true
+		}
+	}
+	if !found {
+		t.Fatal("expected seeded customer Alice Johnson in export")
+	}
+}
+
+func TestExportRequiresMembership(t *testing.T) {
+	repo := db.NewMemoryRepository()
+	svc := NewService(repo)
+	var buf bytes.Buffer
+	err := svc.WriteCustomersCSV(context.Background(), domain.Principal{Subject: "nobody"}, &buf)
+	if err != ErrTenantMembership {
+		t.Fatalf("expected ErrTenantMembership, got %v", err)
+	}
+	if buf.Len() != 0 {
+		t.Fatal("expected no output on membership failure")
+	}
+}
+