Add bird_flash_calls_client implementation with endpoint builder, request schemas, and validator for managing flash call functionality.

services/nginx/app/classes/selfserve_schema_bootstrap.php

@@ -63,6 +63,7 @@ class selfserve_schema_bootstrap
                 machine_relay_enabled_at DATETIME NULL,
                 machine_start_triggered TINYINT(1) NOT NULL DEFAULT 0,
                 machine_start_triggered_at DATETIME NULL,
+                wash_started_at DATETIME NULL,
                 order_id INT NULL,
                 completed_at DATETIME NULL,
                 metadata_json JSON NULL,
@@ -149,6 +150,11 @@ class selfserve_schema_bootstrap
             'dynamic_images_vehicle_type',
             'ALTER TABLE selfserve_wash_session_tasks ADD COLUMN dynamic_images_vehicle_type INT NULL AFTER buttons'
         );
+        self::ensureColumn(
+            'selfserve_wash_sessions',
+            'wash_started_at',
+            'ALTER TABLE selfserve_wash_sessions ADD COLUMN wash_started_at DATETIME NULL AFTER machine_start_triggered_at'
+        );
 
         self::$initialized = true;
     }