archive: prune stale dirs, move actual content to docs/

Deleted stale (Python-era artifacts, superseded by DB):
- archive/oikos-cards/ (46 files, predecessor to DB entity graph)
- archive/ledger/ (5-line JSONL fragment, superseded by DB audit log)

Moved to docs/ (actual, current architecture docs):
- docs/infrastructure/ — 12 infrastructure docs (network, DNS, mesh,
  SSH, ingress, media-permissions, backups, homelab-context, auto-deploy,
  VPS-hardening, monitoring, check-lifecycle)
- docs/secrets/ — secrets README and rotation runbook
- docs/GLOSSARY.md — 28-term homelab glossary

Added STALE.md markers to hermes-plans/ and secrets-issuance/.
Added MOVED.md pointers in archive sources.
Updated docs/index.md to include new paths.

archive/secrets-sops-backup/MOVED.md

@@ -0,0 +1,10 @@
+# Docs moved to `docs/secrets/`
+
+The secret management procedures and rotation runbook have been moved to
+[`docs/secrets/`](../../docs/secrets/):
+
+- [README.md](../../docs/secrets/README.md) — SOPS/Infisical conventions
+- [rotation.md](../../docs/secrets/rotation.md) — rotation runbook
+
+The encrypted `.yaml` files here are kept as DR fallback only. Do not update
+them — use Infisical for live secret management.