fix: missing Namespace in requirements.yaml for flux-web and nfs-csi

[patrick-hermann-sva]

Bug

Two components are missing Namespace definitions in their requirements.yaml:

apps/flux-web

• Uses ${FLUX_WEB_NAMESPACE:-flux-system} but never creates the Namespace
• Works in practice because flux-system is created during Flux bootstrap
• Also missing a README

infra/nfs-csi

• Uses ${NFS_CSI_NAMESPACE:-kube-system} but never creates the Namespace
• Works in practice because kube-system always exists

Fix

Add Namespace resources to both requirements.yaml files for consistency with all other components:

---
apiVersion: v1
kind: Namespace
metadata:
  name: ${<PREFIX>_NAMESPACE:-<default>}
  labels:
    toolkit.fluxcd.io/tenant: sthings-team

Note: For nfs-csi and flux-web, creating Namespace resources for pre-existing system namespaces is safe (Kubernetes reconciles idempotently).