break-glass SSH: drop port-knock for exposed key-only :52222; version host config

Viktor got locked out of the break-glass path (forgot the port-knock setup) and
deleted the edge-router forwards, then asked to review and redesign it from
scratch.

Root cause of the lockout: the knock added no real security (key-only SSH is
already brute-force-proof) and its only benefit — hiding the port — came at the
cost of a circular dependency. The knock sequence lived only in in-cluster
Vault, which is unreachable in the exact away/cold scenario break-glass exists
for. So the unlock secret was unavailable precisely when needed.

New model (self-contained, nothing to remember): plain key-only SSH on the
Proxmox host's :52222, openly reachable. The edge router forwards WAN tcp/52222
-> 192.168.1.127:52222 (external port MUST equal internal on the TP-Link AX6000
- it rejects remaps; port 22 itself is reserved). The exposed port trusts only a
dedicated break-glass key via `Match LocalPort` (a leak of any other root key
does not grant internet access), rate-limited (iptables hashlimit) + fail2ban.

- Removed knockd (package + config) and the legacy Synology SSH forward
  (ext 3333 -> .13:22, a needless WAN exposure the original plan wanted gone).
- Fixed the fail2ban jail for Debian 13 (auth logs under sshd-session, not sshd
  - the stock journalmatch silently never banned).
- Versioned the host config in scripts/ (it was applied ad-hoc, never committed)
  and recorded the deliberate Wave-1 "no public-IP" exception in security.md +
  .claude/CLAUDE.md. Superseded the 2026-05-30 port-knock design docs.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

.claude/CLAUDE.md

@@ -178,7 +178,7 @@ Repo IDs: infra=1, Website=2, finance=3, health=4, travel_blog=5, webhook-handle
 Plan in `docs/architecture/security.md` + response playbook in `docs/runbooks/security-incident.md`. Beads epic: `code-8ywc`.
 
 - **Identity allowlist for security rules**: ONLY `me@viktorbarzin.me`. NOT `viktor@viktorbarzin.me`, NOT `emo@viktorbarzin.me` (those don't exist). emo's identity scheme is unknown — ask before assuming.
-- **Source-IP allowlist (K2, K9, V7, S1)**: `10.0.20.0/22`, `192.168.1.0/24` (Proxmox + Sofia LAN), K8s pod CIDR, K8s service CIDR, Headscale tailnet. **Policy: no public-IP access** — Vault, kube-apiserver, PVE sshd must transit LAN or Headscale.
+- **Source-IP allowlist (K2, K9, V7, S1)**: `10.0.20.0/22`, `192.168.1.0/24` (Proxmox + Sofia LAN), K8s pod CIDR, K8s service CIDR, Headscale tailnet. **Policy: no public-IP access** — Vault, kube-apiserver, PVE sshd must transit LAN or Headscale. **One documented exception (2026-06-11): break-glass SSH** — PVE sshd on a WAN-exposed `:52222`, key-only, dedicated break-glass key only (`Match LocalPort`), rate-limited + fail2ban; intentionally cluster-independent so it survives an outage. As-built `docs/runbooks/breakglass-ssh.md`. (Replaced the 2026-05-30 port-knock design — circular Vault dep caused a lockout.)
 - **Response model**: (I) Slack-only daily skim. All security alerts via Loki ruler → Alertmanager → `#security` Slack receiver. Single channel with severity labels inside (critical/warning/info). No paging.
 - **Kyverno policies (wave 1)**: `deny-privileged-containers`, `deny-host-namespaces`, `restrict-sys-admin`, `require-trusted-registries` flip Audit→Enforce with the 31-namespace exclude list (memory id=1970). `failurePolicy: Ignore` preserved. Cosign `verify-images` deferred.
 - **NetworkPolicy default-deny egress (wave 1)**: observe-then-enforce (γ approach) — Calico flow logs cluster-wide + GlobalNetworkPolicy log-only on tier 3+4, build empirical allowlist after 1 week, phased per-namespace enforce starting `recruiter-responder`. Tier 0/1/2 deferred.