I Pxe Template
iPXE Templates are read-only definitions propagated from nico-core into the REST API. Each template has a stable core UUID and a globally unique name; per-site availability is tracked in IpxeTemplateSiteAssociation records rather than on the template row itself. List and retrieve operations return templates reported at sites the caller is authorized for (optionally filtered by siteId). Templated iPXE Operating Systems reference a template by ipxeTemplateId.