M11: implement operational booking lifecycle

backend/app/main.py

@@ -9,6 +9,7 @@ from app.api.routers import (
     audit,
     auth,
     bookings,
+    customers,
     dashboard,
     data_quality,
     demo,
@@ -90,6 +91,7 @@ app.include_router(auth.router)
 app.include_router(dashboard.router)
 app.include_router(vehicles.router)
 app.include_router(bookings.router)
+app.include_router(customers.router)
 app.include_router(audit.router)
 app.include_router(data_quality.router)
 app.include_router(workflows.router)