fix: sync n8n app before namespace resources

[arch-err]

Summary

• Reverted the broad sync-wave model change; the hardcoded namespace list was rot and has been removed.
• Keeps only the original n8n-specific mitigation currently on this branch: sync Application/n8n at wave -1 before parent-rendered n8n namespace resources.

Verification

• helm lint kubernetes/platform -f kubernetes/infra.yaml
• helm template kubernetes/platform -f kubernetes/infra.yaml

Note

This PR is intentionally narrow again. A proper cluster-wide prerequisite/namespace sync-wave model needs a separate design, not a hardcoded namespace denylist.