Phase 6: replace app template with the vet sample domain + jobs slice, pipelines and worker

- templates/app now carries the vet server (parents/pets/treatments/vets/appointments)
- added domain/jobs slice with /jobs OpenAPI paths and Job schema (x- extensions)
- added pipelines/shared scaffold (loader, ports, registry) and the
  appointment_reminder family; worker.py dispatches jobs by kind
- wired init.py, config.py worker knobs, .env.example, docker-compose worker
- unit tests for jobs routes, the pipeline family and worker dispatch (12 passing)

standards/src/templates/app/main.py

@@ -52,7 +52,7 @@ async def lifespan(app: OpenAPIFirstApp):
 app = OpenAPIFirstApp(
     openapi_path="openapi.yaml",
     routes_module=openapi_routes,
-    title="App Template API",
+    title="Veterinary Clinic API",
     version="0.1.0",
     lifespan=lifespan,
 )