Add `AuthentikForwardAuthFallbackActive` Prometheus alert: fires on
sustained 401/s spike on the websecure entrypoint (>5/s for 5m), which
is the symptom of the auth-proxy Emergency-Access fallback firing —
in turn caused by zero ready endpoints on the outpost service.
Why this rule and not `kube_endpoint_address_available == 0`:
kube-state-metrics endpoint metrics exist as series names but never
have current values in this Prometheus pipeline (something is dropping
them silently). Detecting the failure at the edge via Traefik is more
reliable than instrumenting the broken middle.
Also fix the pre-existing `AuthentikOutpostForwardAuth400Spike` regex
— the service label is `authentik-ak-outpost-...`, not
`authentik-authentik-outpost-...`, so the alert never matched any
series and never could have fired. Verified in Prometheus before/after
the fix.
Add an "Upgrade Validation Checklist" section to
`.claude/reference/authentik-state.md` with the seven-step smoke test
to run after Authentik chart bumps, provider bumps, or outpost pod
recreation. Covers the brittle surfaces (Service selector, JSON
patches, postgres backend wiring, access_token_validity TTL, edge
auth flow, plan-to-zero).
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