feat(catalog): class template editing

Templates were delete-and-recreate only. Adds PUT
/v1/catalog/class-templates/{id} across repository, service (sharing
the create-time validation), route, spec, and client; the classes tab
gets a pencil action that loads the row into the form with a
save/cancel affordance.

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

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

apps/backend/internal/catalog/service.go

@@ -1050,15 +1050,9 @@ func (s *Service) CreateClassTemplate(ctx context.Context, principal domain.Prin
 		return domain.ClassTemplate{}, ErrTenantMembership
 	}
 
-	title := strings.TrimSpace(req.Title)
-	if len(title) < 1 || len(title) > 120 {
-		return domain.ClassTemplate{}, fmt.Errorf("%w: title must be between 1 and 120 characters", ErrInvalidInput)
-	}
-	if req.DurationMinutes < 1 || req.DurationMinutes > 1440 {
-		return domain.ClassTemplate{}, fmt.Errorf("%w: durationMinutes must be between 1 and 1440", ErrInvalidInput)
-	}
-	if req.Capacity < 1 || req.Capacity > 500 {
-		return domain.ClassTemplate{}, fmt.Errorf("%w: capacity must be between 1 and 500", ErrInvalidInput)
+	title, err := validateClassTemplateInput(req)
+	if err != nil {
+		return domain.ClassTemplate{}, err
 	}
 
 	rec, err := s.repo.CreateClassTemplate(ctx, db.CreateClassTemplateParams{
@@ -1372,3 +1366,48 @@ func (s *Service) sendBookingEmail(booking db.BookingRecord, promoted bool) {
 		s.notificationService.SendBookingCancellation(ctx, data)
 	}
 }
+
+func (s *Service) UpdateClassTemplate(ctx context.Context, principal domain.Principal, templateID string, req domain.UpsertClassTemplateRequest) (domain.ClassTemplate, error) {
+	membership, err := s.repo.GetTenantMembershipBySubject(ctx, principal.Subject)
+	if err != nil {
+		return domain.ClassTemplate{}, ErrTenantMembership
+	}
+	if err := s.requireTenantClassTemplate(ctx, membership.Tenant.ID, templateID); err != nil {
+		return domain.ClassTemplate{}, err
+	}
+	title, err := validateClassTemplateInput(req)
+	if err != nil {
+		return domain.ClassTemplate{}, err
+	}
+	rec, err := s.repo.UpdateClassTemplate(ctx, templateID, db.CreateClassTemplateParams{
+		TenantID:        membership.Tenant.ID,
+		Title:           title,
+		DurationMinutes: req.DurationMinutes,
+		Capacity:        req.Capacity,
+	})
+	if err != nil {
+		return domain.ClassTemplate{}, err
+	}
+	return domain.ClassTemplate{
+		ID:              rec.ID,
+		TenantID:        rec.TenantID,
+		Title:           rec.Title,
+		DurationMinutes: rec.DurationMinutes,
+		Capacity:        rec.Capacity,
+		CreatedAt:       rec.CreatedAt,
+	}, nil
+}
+
+func validateClassTemplateInput(req domain.UpsertClassTemplateRequest) (string, error) {
+	title := strings.TrimSpace(req.Title)
+	if len(title) < 1 || len(title) > 120 {
+		return "", fmt.Errorf("%w: title must be between 1 and 120 characters", ErrInvalidInput)
+	}
+	if req.DurationMinutes < 1 || req.DurationMinutes > 1440 {
+		return "", fmt.Errorf("%w: durationMinutes must be between 1 and 1440", ErrInvalidInput)
+	}
+	if req.Capacity < 1 || req.Capacity > 500 {
+		return "", fmt.Errorf("%w: capacity must be between 1 and 500", ErrInvalidInput)
+	}
+	return title, nil
+}