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/db/repository.go

@@ -32,6 +32,7 @@ type Repository interface {
 	ListClassTemplatesByTenant(ctx context.Context, tenantID string) ([]ClassTemplateRecord, error)
 	GetClassTemplateByID(ctx context.Context, templateID string) (ClassTemplateRecord, error)
 	CreateClassTemplate(ctx context.Context, params CreateClassTemplateParams) (ClassTemplateRecord, error)
+	UpdateClassTemplate(ctx context.Context, templateID string, params CreateClassTemplateParams) (ClassTemplateRecord, error)
 	DeleteClassTemplate(ctx context.Context, templateID string) error
 	ListBookingsByTenantBetween(ctx context.Context, tenantID string, from time.Time, to time.Time) ([]BookingRecord, error)
 	CreateBooking(ctx context.Context, params CreateBookingParams) (CreatedBooking, error)
@@ -1311,6 +1312,18 @@ func (r *MemoryRepository) CreateClassTemplate(_ context.Context, params CreateC
 	return record, nil
 }
 
+func (r *MemoryRepository) UpdateClassTemplate(_ context.Context, templateID string, params CreateClassTemplateParams) (ClassTemplateRecord, error) {
+	for index := range r.classTemplates {
+		if r.classTemplates[index].ID == templateID {
+			r.classTemplates[index].Title = params.Title
+			r.classTemplates[index].DurationMinutes = params.DurationMinutes
+			r.classTemplates[index].Capacity = params.Capacity
+			return r.classTemplates[index], nil
+		}
+	}
+	return ClassTemplateRecord{}, pgx.ErrNoRows
+}
+
 func (r *MemoryRepository) DeleteClassTemplate(_ context.Context, templateID string) error {
 	for i, template := range r.classTemplates {
 		if template.ID == templateID {