feat(cloudflared): Cloudflare Tunnel connector, Phase 1 (isolated, no traffic change)

Adds platform/cloudflared: a locally-managed tunnel whose ingress rules live in
git. LAN/VPN-only hosts (plex, plex-vip, jackett, pihole, pihole-dns, semaphore,
qbittorrent, radarr, sonarr, headlamp, unifi, crafty-mc) map to 404. The apex
and *.home go to cilium-gateway-shared.gateway over TLS with matchSNItoHost.
Last comes a catch-all 404. Nothing routes to the Kubernetes API.

- 2-replica Deployment, hard node spread, non-root, pinned digest, PDB
- default-deny plus an egress CNP: Cloudflare edge 7844/443, the Gateway, and
  Gateway backends by gateway-access=shared minus the LAN-only namespaces
  (needed because of the CVE-2025-30162 L7LB egress re-check)
- PodMonitor plus two alerts that fire on absent series, with promtool tests
- its own Flux Kustomization (dependsOn platform-config, wait:false, nothing
  depends on it), plus SOPS decryption patches in both overlays
- placeholder credentials (SOPS-encrypted) so it can merge before enrolment
- L0 cloudflared-ingress-rules, and a cloudflared_ scrape owner
- runbooks/cloudflare-tunnel.md and decisions/2026-11-08-cloudflare-tunnel.md

Co-Authored-By: Claude Opus 5.5 <[email protected]>

platform/cloudflared/alerts.yaml

@@ -0,0 +1,64 @@
+---
+# Alert rules for the Cloudflare Tunnel connector.
+#
+# THE DESIGN CONSTRAINT: NEITHER RULE MAY GO QUIET WHEN ITS OWN DATA DISAPPEARS. The repo has
+# shipped self-silencing rules before (a bare `up{}` that clears exactly when scraping breaks), so:
+#
+#   * CloudflaredTunnelDown reads `cloudflared_tunnel_ha_connections` — the per-replica gauge of
+#     live edge connections — and falls back to `vector(0)` when NO such series exists. A dead
+#     tunnel, zero pods, a broken PodMonitor, or a NetworkPolicy that drops the scrape all make the
+#     series absent, and all of them FIRE rather than read as healthy.
+#   * CloudflaredReplicasDegraded reads kube-state-metrics, which does not depend on cloudflared
+#     being scrapable at all, and has the same `vector(0)` fallback.
+#
+# Both directions are pinned by the companion alerts.promtool-test.yaml (healthy is quiet; absent
+# series fires; working-then-broken re-fires).
+#
+# NOTE FOR PHASE 1: until the operator completes runbooks/cloudflare-tunnel.md steps 1-5 the
+# Deployment cannot connect and CloudflaredTunnelDown fires. That is the honest state — the tunnel
+# is not serving — and nothing routes through it yet, which is why both rules are `warning`.
+# Raise TunnelDown to `critical` in the change that points public DNS at the tunnel.
+apiVersion: monitoring.coreos.com/v1
+kind: PrometheusRule
+metadata:
+  name: cloudflared
+  namespace: cloudflared
+  labels:
+    app.kubernetes.io/name: cloudflared
+spec:
+  groups:
+    - name: platform-health.cloudflare-tunnel
+      rules:
+        - alert: CloudflaredTunnelDown
+          # Sum of live edge connections across every replica. `or on() vector(0)` turns an EMPTY
+          # result (nothing scraped) into 0 so it fires instead of evaluating to no series.
+          expr: (sum(cloudflared_tunnel_ha_connections{namespace="cloudflared"}) or on() vector(0)) < 1
+          # 10m rides out a rolling update and a Cloudflare edge reconnect, not a real outage.
+          for: 10m
+          labels:
+            severity: warning
+          annotations:
+            summary: Cloudflare Tunnel has no healthy edge connections
+            description: >-
+              No cloudflared replica reports a live connection to the Cloudflare edge (or none is
+              being scraped at all). Every hostname routed through the tunnel is unreachable from
+              the internet. Before the operator has enrolled the tunnel this is expected.
+            runbook_url: "https://${BASE_DOMAIN}/runbooks/cloudflare-tunnel"
+
+        - alert: CloudflaredReplicasDegraded
+          # Fewer than the 2 replicas deployment.yaml asks for are Available — the tunnel has lost
+          # its HA, and the next node drain or reboot takes it down. Keep `2` in step with
+          # spec.replicas. Absent series (kube-state-metrics gone, Deployment deleted) -> 0 -> fires.
+          expr: >-
+            (max(kube_deployment_status_replicas_available{namespace="cloudflared",deployment="cloudflared"})
+            or on() vector(0)) < 2
+          for: 15m
+          labels:
+            severity: warning
+          annotations:
+            summary: cloudflared has fewer than 2 available replicas
+            description: >-
+              The cloudflared Deployment has fewer than two Available replicas, so the tunnel has
+              no redundancy (or is down entirely). Check for unenrolled credentials, a node that
+              cannot schedule the hard-spread pod, or an image pull failure.
+            runbook_url: "https://${BASE_DOMAIN}/runbooks/cloudflare-tunnel"