feat(bookings): customer self-service rebooking with real slot picker

CustomerBookingView now carries tenantSlug/serviceId/staffId/
classSessionId so the manage page can query live availability; class
bookings resolve their session title as the display label. Reschedule
rejects waitlisted/completed bookings and session-bound class bookings
(400), collapsing a dead branch in the appointment path.

The manage page reschedule dialog replaces free-form date/time inputs
with a date → availability-slot picker filtered to appointment mode,
so customers can only move to a genuinely free slot with the correct
duration; 409 surfaces "slot just taken". Actions are status-gated:
reschedule for confirmed/pending appointments, cancel for live
bookings, explanatory note for class bookings.

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

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

apps/backend/internal/bookings/customer_service.go

@@ -73,6 +73,12 @@ func (s *CustomerService) managementURL(booking db.BookingRecord) string {
 }
 
 func (s *CustomerService) descriptors(ctx context.Context, booking db.BookingRecord) (serviceName string, locationName string) {
+	if booking.ServiceID == nil && booking.ClassSessionID != nil {
+		// Class bookings carry no service; the session title is the label.
+		if session, err := s.repo.GetClassSessionByID(ctx, *booking.ClassSessionID); err == nil {
+			serviceName = session.Title
+		}
+	}
 	if booking.ServiceID != nil {
 		if services, err := s.repo.ListServicesByTenant(ctx, booking.TenantID); err == nil {
 			for _, service := range services {
@@ -119,6 +125,10 @@ func (s *CustomerService) GetBookingByReference(ctx context.Context, reference s
 		CustomerEmail:    booking.CustomerEmail,
 		Service:          serviceName,
 		BusinessName:     tenant.Name,
+		TenantSlug:       tenant.Slug,
+		ServiceID:        booking.ServiceID,
+		StaffID:          booking.StaffID,
+		ClassSessionID:   booking.ClassSessionID,
 		StartsAt:         booking.StartsAt,
 		EndsAt:           booking.EndsAt,
 		Location:         locationName,
@@ -142,6 +152,18 @@ func (s *CustomerService) RescheduleBooking(ctx context.Context, reference strin
 		return ErrBookingCancelled
 	}
 
+	// Only live bookings may move: waitlisted entries sit in a queue tied to
+	// their session, and completed bookings are history.
+	if booking.Status == "waitlisted" || booking.Status == "completed" {
+		return ErrInvalidReschedule
+	}
+
+	// Class bookings are bound to their session window; moving to another
+	// session means cancelling and booking again.
+	if booking.ClassSessionID != nil {
+		return ErrInvalidReschedule
+	}
+
 	newStartsAt, err := time.Parse(time.RFC3339, req.NewStartsAt)
 	if err != nil {
 		return ErrInvalidReschedule
@@ -174,16 +196,14 @@ func (s *CustomerService) RescheduleBooking(ctx context.Context, reference strin
 		}
 	}
 
-	// Appointments must land inside bookable hours and off blocked days;
-	// class bookings keep their session-defined window.
-	if booking.ClassSessionID == nil {
-		tenant, err := s.repo.GetTenantByID(ctx, booking.TenantID)
-		if err != nil {
-			return err
-		}
-		if err := validateAppointmentTarget(ctx, s.repo, tenant, booking.StaffID, booking.LocationID, newStartsAt, newEndsAt); err != nil {
-			return ErrInvalidReschedule
-		}
+	// Appointments must land inside bookable hours and off blocked days.
+	// Class bookings never reach this point — rejected above.
+	tenant, err := s.repo.GetTenantByID(ctx, booking.TenantID)
+	if err != nil {
+		return err
+	}
+	if err := validateAppointmentTarget(ctx, s.repo, tenant, booking.StaffID, booking.LocationID, newStartsAt, newEndsAt); err != nil {
+		return ErrInvalidReschedule
 	}
 
 	if err := s.repo.RescheduleBooking(ctx, booking.ID, newStartsAt, newEndsAt); err != nil {

apps/backend/internal/bookings/customer_service_test.go

@@ -111,3 +111,41 @@ func TestRescheduleRejectsConflictingSlot(t *testing.T) {
 		t.Fatalf("expected ErrBookingConflict, got %v", err)
 	}
 }
+
+func TestRescheduleRejectsClassWaitlistedAndCompleted(t *testing.T) {
+	repo := db.NewMemoryRepository()
+	svc := NewCustomerService(repo, nil, "http://localhost:3000")
+	sessionID := "4bf74c12-44dd-45ca-86bb-b104f16f2435"
+	future := time.Now().Add(48 * time.Hour)
+
+	cases := []struct {
+		name      string
+		status    string
+		sessionID *string
+	}{
+		{"class booking", "confirmed", &sessionID},
+		{"waitlisted booking", "waitlisted", &sessionID},
+		{"completed booking", "completed", nil},
+	}
+	for i, tc := range cases {
+		_, err := repo.CreateBooking(context.Background(), db.CreateBookingParams{
+			TenantID:       "5d6b3551-0a3e-4b86-bdf0-e9df20a47148",
+			ClassSessionID: tc.sessionID,
+			StartsAt:       future,
+			EndsAt:         future.Add(time.Hour),
+			Status:         tc.status,
+			Reference:      "BOK-RS-" + string(rune('A'+i)),
+			ManageToken:    "tok",
+		})
+		if err != nil {
+			t.Fatalf("%s: create booking: %v", tc.name, err)
+		}
+		err = svc.RescheduleBooking(context.Background(), "BOK-RS-"+string(rune('A'+i)), domain.RescheduleBookingRequest{
+			NewStartsAt: future.Add(2 * time.Hour).Format(time.RFC3339),
+			NewEndsAt:   future.Add(3 * time.Hour).Format(time.RFC3339),
+		}, "tok")
+		if err != ErrInvalidReschedule {
+			t.Fatalf("%s: expected ErrInvalidReschedule, got %v", tc.name, err)
+		}
+	}
+}

apps/backend/internal/domain/models.go

@@ -490,6 +490,12 @@ type CustomerBookingView struct {
 	CustomerEmail string    `json:"customerEmail"`
 	Service       string    `json:"service"`
 	BusinessName  string    `json:"businessName"`
+	TenantSlug    string    `json:"tenantSlug,omitempty"`
+	ServiceID     *string   `json:"serviceId,omitempty"`
+	StaffID       *string   `json:"staffId,omitempty"`
+	// ClassSessionID identifies session-bound bookings; they cannot be
+	// rescheduled to arbitrary times (see RescheduleBooking).
+	ClassSessionID *string  `json:"classSessionId,omitempty"`
 	StartsAt      time.Time `json:"startsAt"`
 	EndsAt        time.Time `json:"endsAt"`
 	Location      string    `json:"location"`