Rancher: Cross-Cluster Secret Leakage via Namespace projectId Annotation Spoofing

A flaw was found in Rancher Manager. Project Secrets were propagated into a namespace based only on its `field.cattle.io/projectId` annotation, without verifying that the referenced project belonged to the same downstream cluster. A user able to create namespaces on one cluster could set the annotation to a project ID from another cluster and have that project's secrets copied into a namespace under their control.

This issue affects Rancher: before 2.15.1.