Add exception handling for cleaner relay activation in self-serve lanes

- Include `\Throwable` in docstring for better error documentation.
- Implement `turnOnCleanerRelayForWashStart` in the wash start process.

services/nginx/app/modules/selfserve/traits/selfserve_lane_command_t.php

@@ -464,6 +464,7 @@ trait selfserve_lane_command_t
      * @param selfserve_lane_command_arguments $arguments The arguments for the command
      * @return selfserve_lane|selfserve_lane_command_t
      * @throws Exception If the command cannot be executed
+     * @throws \Throwable
      */
     public function execute(selfserve_lane_command $command, selfserve_lane_command_arguments $arguments): self
     {
@@ -517,6 +518,7 @@ trait selfserve_lane_command_t
                     // Open the entrance port before marking the lane occupied. Gateway timeouts are
                     // ambiguous because the relay may already have received the pulse.
                     $this->openEntrancePortForWashStart();
+                    $this->turnOnCleanerRelayForWashStart();
                 } catch (\Throwable $e) {
                     $this->setCustomerNumber($previous_customer_number);
                     $this->setLicensePlate($previous_license_plate);